TECHNICAL AREA

The present invention concerns a method to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine. The invention concerns also a computer program product comprising program code for a computer to implement a method according to the invention. The invention concerns also an arrangement to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine and a motor vehicle that is equipped with the arrangement.

BACKGROUND

There are today in many countries strict regulations with respect to the emission of undesired gases and particles from vehicles. Vehicle manufacturers are working continuously to improve post-processing systems to make it possible to reduce further the amount of undesired emissions in exhaust gases. Undesired gases formed in vehicle engines for which restrictions have been imposed, are nitrogen oxides {NOx}.

One method to reduce the amount of NOx in exhaust gases is to use what is known as a "post-processing system", for example an SCR system (where "SCR" is an abbreviation for "selective catalytic reduction"). This system comprises an SCR catalyser and a dosage unit for a suitable reducer agent, for example a urea -based aqueous solution. The said reducer agent and NOx gas can react in the catalyser and be converted to nitrogen and water.

The amount of NOx in exhaust gases is detected with at least one NOx sensor that is placed in an exhaust gas passage at the exhaust gas system, for example downstream of the SCR catalyser. The sensor is used to detect the amount of IMOx in exhaust gases that are emitted from the vehicle. The signals from the NOx sensor can be used, for example, to control the dosage of the said reducer agent that is used in the SCR system or as a basis on which to generate error codes when the amount of MOx is higher than a certain predetermined value.

When the amount of MOx detected in the exhaust gases is higher than a certain predetermined value, the driver is instructed to drive the vehicle to a workshop in order to solve the problem, A high detected value of NOx may have a number of causes such as the quality of the said reducer agent, a defective SCR system, defective sensors, etc. Measures are carried out in the workshop in order to investigate and correct the cause of the high detected values of !MOx in the exhaust gases. One common measure that is carried out when too high a value of the NOx level has been detected, is to check the function of the NOx sensor. This is carried out by operating the engine according to a certain predetermined programme and detecting by means of the NOx sensor the amount of NOx in the exhaust gases during the said programme. The levels of NOx detected in the exhaust gases are compared with calculated NOx levels. The calculated NOx levels are obtained from a calculation model in which various factors that influence the NOx level in exhaust gases, such as the amount of fuel injected, the operating conditions of the engine, etc., are considered. If the measured NOx values differ from the calculated NOx values by more than a certain predetermined value, it is concluded that the NOx sensor is defective and the NOx sensor is exchanged.

Since it is complicated to obtain reliable NOx levels by calculation, a NOx sensor may, after a comparison between the calculated NOx value and the detected NOx value, sometimes be erroneously identified as defective and thus exchanged unnecessarily.

Operating an engine at a vehicle at its optimal combustion is desirable since the amount of undesired emissions and the fuel consumption can in this way be minimised. A carefully balanced amount of fuel relative to the air in the engine corresponds to essentially optimal combustion in the engine. In order to obtain an estimation of how optimal the combustion of the engine is, the level of oxygen in an exhaust gas passage from the said engine can be detected. This can be carried out by means of what is known as a "lambda sensor". The amount of fuel relative to air in the exhaust gas passage can be calculated with the aid of the detected amount of oxygen in the exhaust gas passage. The amount of fuel relative to air in the exhaust gas passage may be a measure of how optimal the combustion of the engine is. Depending on the level of oxygen that is detected in the exhaust gas passage, the fuel injection in the engine can be regulated such that an optimal combustion is obtained, and thus such that a lower amount of emissions is created. When a level of oxygen detected in the exhaust gases deviates from a predetermined interval within which the level of oxygen is considered to be normal, an appropriate error code can be generated. Alternatively, the driver can be instructed to drive the vehicle to a workshop or service station in order to solve the problem. A detected level of oxygen that exceeds or that lies below the said normal level of oxygen may have several different causes, such as, for example, an erroneous amount of dosed fuel, a defective lambda sensor, etc. Measures are carried out in the workshop to investigate and correct the cause of the level of oxygen detected that lies below or exceeds the said normal level of oxygen. One common measure is to check the function of the lambda sensor. This is normally carried out by operating the engine according to a certain predetermined programme and detecting by means of the lambda sensor the level of oxygen in the exhaust gas passage. The level of oxygen detected can be used to calculate the amount of fuel relative to air in the exhaust gases during the said programme. The calculated levels of fuel relative to air in the exhaust gases, which are calculated with the aid of the measured levels of oxygen, will be demoted in this description by "the detected levels of fuel relative to air in the exhaust gases". These detected levels of fuel relative to air in the exhaust gases are compared with a calculated value of the amount of fuel relative to air in which factors such as the amount of dosed fuel, the operating condition of the engine, etc. are taken into consideration. If the amount of fuel relative to air detected with the aid of the lambda sensor differs from the calculated amount of fuel relative to air by more than a certain specified value, it is concluded that the lambda sensor is defective, and the lambda sensor is exchanged.

Since it is complicated to obtain a reiiabie amount of fuel relative to air by calculation, a lambda sensor may, after a comparison between the calculated amount of fuel relative to air and the detected amount of fuel relative to air, sometimes be erroneously identified as defective and thus exchanged unnecessarily.

SUMMARY OF THE INVENTION

One purpose of the present invention is to provide a new and advantageous method to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine.

A second purpose of the invention is to provide a new and advantageous method and a new and advantageous computer program to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine.

A further purpose of the invention is to provide a method, an arrangement and a computer program in order to achieve a reiiabie and user-friendly determination of the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine.

A further purpose of the invention is to provide a method, an arrangement and a computer program in order to achieve a time-efficient determination of the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine. A further purpose of the invention is to provide a method, an arrangement and a computer program in order to reduce the risk that a sensor arranged to determine the level of a component in the exhaust gases from an engine is erroneously identified as defective or is exchanged unnecessarily.

Certain of these purposes are achieved with a method to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine according to claim 1. Certain of these purposes are achieved with an arrangement according to claim 8, Advantageous embodiments are specified med reference to the non-independent claims.

According to one aspect of the present invention, a method is provided to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine, including the following steps:

-- to expose the said sensor to a reference gas, other than the said exhaust gases, with a known level of the said component;

- to determine a level of the said component in the said reference gas by means of the said sensor;

- to compare the level determined in this way with the said known level with respect to the said component; and

- to assess the said function on the basis of the result of the said comparison.

By comparing the level of a component in the said reference gas determined by means of the sensor with the known level of the said component in the said reference gas, it can be determined in a robust, accurate and time-efficient manner whether the said sensor is defective or not. it is advantageous that the said reference gas has an accurately measured level of the said component. This level may be measured by a freely chosen suitable sensor, for example, at a manufacturing location at which the said reference gas is prepared. Since the known level of the said component of the said reference gas is determined with very high accuracy, the function of the sensor can be determined with very high reliability in the cases in which too high or too low a level of the said component in an exhaust gas passage has been detected. This leads to major advantages since it increases the probability that the true cause of the detected too high or too low level of the said component can be identified, and when the cause of the detected levels is investigated a sensor that is correct will not, according to the method according to the invention, be exchanged, which entails a saving in costs. Since the said method can be rapidly carried out, time is saved that can be used to investigate further the cause of the fault that generated the detected too high or too low levels of the said component in the said exhaust gas passage.

According to one aspect of the invention, the said sensor is considered to be correct if the level determined by means of the sensor lies within a certain predetermined interval, which interval is associated with the said known level of the said component in the reference gas. According to one example, in which the said component is !MOx, the said known level can be 900 ppm. The said interval can then, according to one example, be between 895 and 905 ppm. The said interval may, as an alternative, be between 870 and 930 ppm. The said interval can, according to one example, be defined as +/-S% of the said known level. The said interval can, according to one example, be defined as +/-10% of the said known level.

According to one aspect of the invention, the said sensor is exposed to a reference gas for a period of time between 1 and 5 minutes. According to one aspect of the invention, the said sensor is exposed to a reference gas for a suitable period of time, for example 1, 3, 5, 7 or 10 minutes.

According to one aspect of the invention, the said sensor is a NOx sensor. According to one aspect of the invention, the said sensor is a lambda sensor. In this way, a flexible method is provided in which levels of different components can be determined in order to determine in a reliable manner the function of a relevant sensor.

The method may comprise the foi!owing step:

- after the step of exposing the said sensor to a first reference gas with a known level of the said component,

- to expose the said sensor to at least one further reference gas, where the said further reference gas has a known level of the said component that differs from the level in the said first reference gas.

According to one aspect of the invention, the said function at at least two sensors can be determined at the same time by exposing during essentially the same period of time the said at least two sensors to the reference gas adapted for each sensor. By determining the function of the relevant sensor at the same time, a time- efficient method is achieved.

According to one aspect of the invention, the said component is NOx. According to one aspect of the invention, the said component is oxygen.

Since the function of different types of sensor can be determined according to the method according to the invention, a flexible method is achieved.

The method may comprise the following steps:

- to expose the said sensor to a first reference gas with a known level of the said component;

- to expose the said sensor to at least one further reference gas, where the said further reference gas has a level of the said component that differs from the level in the said first reference gas. According to one design, the said reference gas is air. A suitable number of reference gases can be used according to the method according to the invention in order to determine the function of the said sensor. Each reference gas may contain an accurately determined known concentration of the said component. Such a reference gas may, therefore, comprise a concentration of the said component that is essentially zero.

According to one aspect of the invention, the said sensor is exposed to at least two reference gases with different known levels of the said component. Exposures of the, at least two, reference gases preferably take place at different times in order to ensure that only one reference gas is exposed to the said sensor at any one time.

According to one example, the said sensor is exposed to a first reference gas demonstrating a known level of MGx of 0 ppm, and a second reference gas with a known level of NOx of 900 ppm. According to one embodiment, the range of measurement of the sensor is essentially covered by the said known levels of NOx. According to one embodiment, two reference gases can be used according to the method according to the invention, which two reference gases include a known level of the said component at a lower part and a higher part, respectively, of the range of measurement of the sensor.

According to one example, the said sensor is exposed to three reference gases with different known levels of the said component. According to one embodiment, the said three reference gases have 0, 500 and 1000 ppm, respectively, of NOx. According to one embodiment, the range of measurement of the sensor is covered by the said known levels of NOx.

According to one example, the said sensor is exposed to ten reference gases with different known levels of NOx. According to one embodiment, the said ten reference gases have, for example, 0, 100, 200, 300, 400, 500, 600, 700, 800, 900 and 1000 ppm, respectively, of NOx. According to this embodiment, the said complete range of measurement of the sensor is tested. According to one embodiment, the range of measurement of the sensor is covered by the said known levels of NOx.

According to one example, measurements are carried out for at least one reference gas with a known level of NOx up to 3000 ppm.

According to one aspect of the said invention, the said, different known levels of the said component are selected such that they in this way cover essentially the complete range of measurement of the sensor.

According to one aspect of the present invention, a range of measurement of a sensor may be, in the case in which the said sensor is a NOx sensor, between 0 and 3000 ppm.

According to on design, one reference gas corresponds to a known level of NOx of 0 ppm of air. The said air may consist of workshop air, outdoor air, or chemical air. By using air as reference gas, a cost-effective method can be achieved since it is not necessary to prepare this reference gas. The said component in air does not need to be measured by a control sensor, since the said level is already known.

According to the method according to the invention, a reliable result from the determination of the function of a sensor is obtained. According to the method according to the invention, a determination of the function of a sensor can be carried out in a time-efficient manner.

According to one aspect of the present invention, a range of measurement of a sensor may be, in the case in which the said sensor is lambda sensor, between 0.8 and 1.7. The method may comprise the following step:

- to maintain the said sensor connected such that it transfers signals to a control system at the said engine in the same manner as during conventional use of the sensor.

The said sensor is connected such that it transfers signals to a control system at the said engine during normal operation. Signals that include information about the detected level of the said component are transmitted to the control system, which is adapted to determine whether the said level is to form the basis for generating a suggestion for an inspection or service measure or not. Signals that include information about the detected level of the said component are transmitted to the control system, which is adapted to determine whether the said level is to form the basis for generating an error code or not.

By maintaining the said sensor connected such that it transfers signals to a control system at the said engine in the same manner as during conventional use of the sensor, a rapid and simple method according to the invention is achieved. By the sensor being connected to the said control system during the method, time is saved since the said sensor does not need to be disconnected and connected to another control system or measuring equipment.

With the aid of the said connection that transfers signals, the said control system can prepare the sensor for the detection of the said component of a reference gas, by, for example, heating the sensor to a predetermined suitable temperature.

According to one aspect of the present invention, the said exposure of a reference gas to the said sensor is carried out with the said sensor arranged at its conventional location at the exhaust gas passage or arranged external to the said exhaust gas passage. According to one design, the said sensor is connected such that it transfers signals to a control unit at the vehicle, for example the control system of the engine, during the said exposure of a reference gas.

According to one aspect of the present invention, the said exposure is carried out with the said sensor arranged at its conventional location at the exhaust gas passage. According to this aspect, a reference gas is introduced into the said exhaust gas system such that the said sensor is exposed to the said reference gas in order to allow adequate detection of the said level of the said component.

According to one aspect of the present invention, the said exposure is carried out with the said sensor arranged external to the said exhaust gas passage. According to one design, the said sensor is connected such that it transfers signals to the control system of the engine, and the measurement is this in this way carried out in the vicinity of the said exhaust gas passage, but external to the said exhaust gas passage.

The method can be implemented in existing motor vehicles. Program code to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine according to the invention can be installed in a control unit at the vehicle during manufacture of the same. A purchaser of the vehicle can thus he given the opportunity of choosing the function of the method as an optional extra. Alternatively, program code to carry out the method according to the invention to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine is installed in a control unit at the vehicle during upgrade at a service station. The program code in this case can be loaded into a memory in the control unit.

Program code to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine may be updated or exchanged. Furthermore, different parts of the program code to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine may be exchanged independently of each other. This modular configuration is advantageous from the point of view of maintenance.

According to one aspect of the present invention, a method is provided to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine, comprising:

- a sensor arranged at an exhaust gas passage arranged to detect the said level of a component of a reference gas, other than the said exhaust gases, with a known level of the said component;

- means adapted to determine a level of the said component of the said reference gas by means of the said sensor;

- means adapted to compare the level determined in this way with the said known level with respect to the said component; and

-- means adapted to assess the said function on the basis of the result of the said comparison.

According to one aspect of the present invention, an arrangement is provided to determine the function of a sensor arranged to determine the level of a component of exhaust gases from an engine, where the said sensor is adapted for exposure to a reference gas, other than the said exhaust gases, with a known level of the said component, and where the said sensor is furthermore adapted to determine a level of the said component in the said reference gas. The arrangement further comprises:

- means adapted to compare the level determined in this way with the said known level with respect to the said component; and

- means adapted to assess the said function on the basis of the result of the said comparison. The arrangement may comprise a sensor, whereby the said sensor is a MOx sensor or a lambda sensor.

The arrangement may comprise:

- means adapted to expose the said sensor to at least two reference gases with different known levels of the said component in order to assess the said function.

The arrangement may comprise:

- means adapted to hold the said sensor in a manner that allows it to be removed, whereby the said means is attached at the said exhaust gas passage in a manner that allows it to be removed.

The arrangement may comprise:

- means adapted to hold the said sensor in a manner that allows it to be removed, whereby the said means is attached at the said exhaust gas passage in a manner that allows it to be removed.

The purposes described above are achieved also with a motor vehicle that comprises the arrangement to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine. The motor vehicle may be a lorry, a bus or a car.

According to one aspect of the invention, a computer program is provided to determine the function of a sensor arranged to determine the level of a component of the exhaust gases from an engine, where the said computer program comprises program code in order to cause an electronic control unit or a second computer connected to the electronic control unit to carry out the steps according to any one of claims 1-7. According to one aspect of the invention, a computer program is provided to determine the function of a sensor arranged to determine the level of a component of the exhaust gases from an engine, where the said computer program comprises program code stored on a medium that can be read by a computer in order to cause an electronic control unit or a second computer connected to the electronic control unit to carry out the steps according to any one of claims 1-7.

According to one aspect of the invention, a computer program product comprising program code is provided stored on a medium that can be read by a computer, in order to carry out the method steps according to any one of claims 1-7, where the said program code is run on an electronic control unit or a second computer connected to the electronic control unit.

Further purposes, advantages and new distinctive features of the present invention will be made clear for one skilled in the arts by the following details, as also during execution of the invention. While the invention is described below, it should be obvious that the invention is not limited to the specific details described. Those skilled in the arts will recognise further applications, modifications and executions within other fields, which lie within the scope of the invention.

BRIEF DESCRIPTION OF DRAWINGS

For a more complete understanding of the present invention and further purposes and advantages of it, reference is now made to the following detailed description, which is to be read together with the accompanying drawings in which the same reference numbers relate to the same parts in the various drawings, and in which:

Figure 1 illustrates schematically a vehicle, according to one embodiment of the invention;

Figure 2a illustrates schematically an arrangement to determine the function of a sensor arranged to determine the level of a component in exhaust gases from an engine, where the said sensor is arranged in an exhaust gas passage that leads exhaust gases from an engine, according to one embodiment of the invention; Figure 2b illustrates schematically one embodiment of the present invention;

Figure 2c illustrates schematically one embodiment of the present invention;

Figure 2d illustrates schematically one embodiment of the present invention;

Figure 2e illustrates schematically one embodiment of the present invention;

Figure 2f illustrates schematically one embodiment of the present invention;

Figure 3a illustrates schematically a drawing, according to one aspect of the invention;

Figure 3b illustrates schematically a drawing, according to one aspect of the invention;

Figure 4a illustrates schematically a flow diagram of a method according to one embodiment of the invention;

Figure 4b illustrates schematically in greater detail a flow diagram of a method according to one aspect of the invention;

Figure 5 illustrates schematically a computer according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to Figure 1, there is shown a side view of a vehicle 100. The vehicle 100 taken as an example consists of a drawing vehicle 110 and a trailer 112. The vehicle may be a heavy vehicle, such as a lorry or a bus. Alternatively, the vehicle may be a car. It should be pointed out that the invention is suitable for application at a freely chosen suitable engine and is thus not limited to motor vehicles.

The method according to the invention and the arrangement according to the invention to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine according to one aspect of the invention are well suited for other platforms than motor vehicles that include an engine, such as, for example, water-going vessels. The water-going vessels may be of any freely chosen type such as, for example, motor boats, vessels, ferries or ships.

The method according to the invention and the arrangement according to the invention to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine according to one aspect of the invention are well suited also, for example, for systems that include, for example, a stone crusher or similar.

The method according to the invention and the arrangement according to the invention to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine according to one aspect of the invention are well suited also, for example, for systems that include at least one of industrial engines and motor-driven industrial robots.

The method according to the invention and the arrangement according to the invention to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine according to one aspect of the invention are well suited also, for various types of power station, such as, for example, an electrical power station that comprises a diesel generator.

The method according to the invention and the arrangement according to the invention to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine according to one aspect of the invention are well suited for a freely chosen suitable motor system that includes an engine such as, for example, a locomotive or another platform. In this document, the term "link" refers to a communication link that may be a physical line, such as an optoelectronic communication line, or a non-physical line, such as a wireless connection, for example a radio link or microwave link. In this document, the term "line" refers to a passage to contain and to transport a fluid, such as, for example, a reducer in fluid form. The line may be a pipe of freely chosen dimension. The line may be of a freely chosen and suitable material, such as, for example, plastic, rubber or metal. in this document, the terms "reducer" and "reducer agent" refer to an agent that is used to react with certain emissions in an SCR system. These emissions may be, for example, NO _x gas. The terms "reducer" and "reducer agent" are used synonymously in this document. The said reducer according to one embodiment is what is known as AdBlue. Naturally, other types of reducer can be used.

With reference to Figure 2a, there is shown an arrangement 299 at the vehicle 100. The arrangement 299 may be arranged in the drawing vehicle 110. The arrangement comprises an engine 206. The said engine 206 is a combustion engine, for example a diesel engine. The said engine 206 may be a suitable engine. The said engine 206 may be powered by, for example, petrol, ethanoi or gas. The said engine 206 is arranged to lead exhaust gases to an exhaust gas passage 290.

The arrangement comprises a first control unit 200. The arrangement 299 comprises according to this example of a container 205 that is arranged to contain a reducer. The container 205 is arranged to contain a suitable amount of reducer and is further arranged such that it can be filled when necessary.

A first line 271 is arranged to lead the reducer to a pump 230 from the container 205, The pump 230 may be a freely chosen suitable pump. The pump 230 may be arranged to be driven by means of an electric motor (not shown in the drawings). The pump 230 may be arranged to pump the reducer up from the container 205 through the first line 271 and to supply the said reducer through a second line 272 to a dosage unit 250.

The dosage unit 250 is arranged to supply the said reducer to the said exhaust gas passage 290 at the vehicle 100. According to this method, an SCR catalyser 270 is arranged downstream of a position at the exhaust gas system at which supply of reducer takes place. The amount of reducer that is supplied into the exhaust gas system is intended to be used in the SCR catalyser in order to reduce the amount of undesired emissions.

According to one design given as an example, what is known as a "three-way catalyser" is provided at the said exhaust gas passage 290. The use of lambda sensors is advantageous in the cases in which the said arrangement 299 includes a three-way catalyser.

A first NOx sensor 255 is arranged for communication with the first control unit 200 over a link L255. The first NOx sensor 255 is arranged to determine continuously a prevalent NOx level HmeasNox in the exhaust gases from the engine 206 at the exhaust gas passage upstream of the said SCR catalyser 270. The first NOx sensor 255 is arranged to send continuously signals S255 comprising information about a prevalent NOx level HmeasNox upstream of the said SCR catalyser 270 to the first control unit 200. The first NOx sensor is arranged such that it can be removed at the exhaust gas passage 290. The first NOx sensor 255 can in this way determine a currently prevalent NOx level HmeasNox in the exhaust gases at the exhaust gas passage 290. The first NOx sensor 255 can in this way determine a currently prevalent NOx level HmeasNox in a reference gas that is supplied to the said exhaust gas passage 290. The first NOx sensor 255 can in this way determine a currently prevalent NOx level HmeasNox in a reference gas external to the said exhaust gas passage 290. The first NOx sensor 255 may be connected such that it transfers signals to the first contro! unit 200, in all cases described.

A second NO _x sensor 265 is arranged for communication with the first control unit 200 over a link L265. The second NO _x sensor 265 is arranged to determine continuously during operation a prevalent NO _x level HmeasNox in the exhaust gases from the engine 206 in the exhaust gas passage 290 downstream of the said SCR cataiyser 270. The second NO _x sensor 265 is arranged to send continuously signals S265 comprising information about a prevalent MO _x level HmeasNox to the first control unit 200. The second NOx sensor is arranged such that it can be removed at the exhaust gas passage 290. The second NOx sensor 265 can in this way determine a currently prevalent NOx level HmeasNox in the exhaust gases at the exhaust gas passage 290. The second NOx sensor 265 can in this way determine a currently prevalent NOx level HmeasNox in a reference gas that is supplied to the said exhaust gas passage 290. The second NOx sensor 265 can in this way determine a currently prevalent NOx level HmeasNox in a reference gas external to the said exhaust gas passage 290. The second NOx sensor 265 may be connected such that it transfers signals to the first contro! unit 200, in all cases described.

The first contro! unit 200 is arranged to communicate with the relevant NOx sensor 255, 265. The level of NOx HmeasNox determined by the NOx sensor in the said reference gas is communicated to the first contro! unit 200, The first contro! unit 200 is arranged to compare the level of NOx HmeasNox determined by the said NOx sensor 255, 265 with the said known level with respect to NOx in the said reference gas. The first control unit 200 is further arranged to determine the function of the said NOx sensor 255, 265 on the basis of the result of the said comparison.

A first lambda sensor 235 is arranged for communication with the first control unit 200 over a link L235. The first lambda sensor 235 is arranged to determine continuously during operation a prevalent oxygen level HmeasOx in the exhaust flow of the engine upstream of the said SCR catalyser 270. The first lambda sensor 235 is arranged to send continuously signals S235 comprising information about a prevalent oxygen level HmeasOx in the exhaust gases upstream of the said SCR catalyser 270 to the first control unit 200. The first lambda sensor is arranged such that it can be removed at the exhaust gas passage 290. The first lambda sensor 235 can in this way determine a currently prevalent level of oxygen HmeasOx in the exhaust gases at the exhaust gas passage 290. The first lambda sensor 235 can in this way determine a currently prevalent oxygen value HmeasOx in a reference gas that is supplied to the said exhaust gas passage 290. The first lambda sensor 235 can in this way determine a currently prevalent oxygen value HmeasOx in a reference gas external to the said exhaust gas passage 290. The first lambda sensor 235 may be connected such that it transfers signals to the first control unit 200, in ail cases described, A second lambda sensor 245 is arranged for communication with the first control unit 200 over a link L245. The second lambda sensor 245 is arranged to determine continuously during operation a prevalent oxygen level HmeasOx in the exhaust flow of the engine downstream of the said SCR catalyser 270. The second lambda sensor 245 is arranged to send continuously signals S245 comprising information about a prevalent oxygen level HmeasOx to the first control unit 200. The second lambda sensor is arranged such that it can be removed at the exhaust gas passage 290. The second lambda sensor 245 can in this way determine a currently prevalent level of oxygen HmeasOx in the exhaust gases at the exhaust gas passage 290. The second lambda sensor 245 can in this way determine a currently prevalent oxygen value HmeasOx in a reference gas that is supplied to the said exhaust gas passage 290. The second lambda sensor 245 can in this way determine a currently prevalent oxygen value HmeasOx in a reference gas external to the said exhaust gas passage 290. The second lambda sensor 245 may be connected such that it transfers signals to the first control unit 200, in ail cases described. According to one design given as an example, the said first lambda sensor 235 is arranged to determine continuously during operation a prevalent oxygen level HmeasOx in the exhaust flow of the engine upstream of what is known as a "three- way catalyser" (not shown in the drawings) arranged in the said exhaust gas passage 290.

According to one design given as an example, the said second lambda sensor 245 is arranged to determine continuously during operation a prevalent oxygen level HmeasOx in the exhaust flow of the engine downstream of what is known as a "three-way catalyser" (not shown in the drawings) arranged in the said exhaust gas passage 290,

The first control unit 200 is arranged to communicate with the relevant lambda sensor 235, 245. The level of oxygen HmeasOx in the said reference gas determined by the lambda sensor is communicated to the first control unit 200. The first control unit 200 is arranged to compare the level of oxygen HmeasOx determined by the said lambda sensor with the said known level of oxygen Ref 1 Ox in the said reference gas. The first control unit 200 is further arranged to determine the function of the said lambda sensor 235, 245 on the basis of the result of the said comparison.

The first control unit 200 is arranged to determine the function of the said sensor 235, 245, 255, 265. The first control unit is arranged to determine the function of the said sensor 235, 245, 255, 265 on the basis of the result of the said comparison, where the said sensor 235, 245, 255, 265 is exposed to a first reference gas Ref 1 Nox, Ref 1 Ox with a known level of the said component and subsequently to at least one further reference gas, where the said further reference gas has a level Ref 2 Nox, Ref 2 Ox of the said component that differs from the level in the said first reference gas. The first control unit 200 is arranged to determine the function of the said sensor 235, 245, 255, 265 on the basis of the result of the said comparison, where the said sensor is exposed to a first reference gas with a known level Ref 1 NQX, Ref 1 Ox of the said component and subsequently to at least one further reference gas, whereby the said different known levels of the said reference gases are selected to cover the range of measurement of the sensor.

According to the method according to the invention, the first control unit 200 is maintained, during the measurement of the said reference gas, connected such that it transfers signals to the said sensor, 235, 245, 255, 265, in the same manner as during conventional use of said sensor 235, 245, 255, 265.

According to one embodiment of the method according to the invention, the said exposure of a reference gas is carried out with the sensor 235, 245, 255, 265 arranged at its conventional location at the exhaust gas passage 290. According to one embodiment of the method according to the invention, the said exposure is carried out with the said sensor 235, 245, 255, 265 arranged external to the said exhaust gas passage 290.

The first control unit 200 is arranged for communication with presentation means 280 over a link L280. The said presentation means 280 may be arranged in a driver's cabin of the vehicle 100. The said presentation means 280 may be fixed mounted in the vehicle 100. The said presentation means 280 may be a mobile electronic unit. The said presentation means 280 may include, for example, a display. The first control unit 200 is arranged to present an error code or other relevant information with respect to the innovative method to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine. The first control unit 200 may be arranged to present by means of the said presentation means 280 a result of the said assessment or determination of whether the said sensor 235, 245, 255, 265 is defective or not. The first contro! unit 200 is arranged for communication with a communication unit 285 through a link L285. The said communication unit 285 may be present at, for example, a service station, workshop, haulier's premises or what is known as a "fleet management system".

The said communication unit 285 may be arranged in a driver's cabin of the vehicle 100, The said communication unit 285 may be fixed mounted in the vehicle 100. The said communication unit 285 may be a mobile electronic unit. The said communication unit 285 may include, for example, a display. The first control unit 200 is arranged to present automatically or on request an error code or other relevant information with respect to the method according to the invention to determine the function of a sensor 235, 245, 255, 265 arranged to determine the level of a component in the exhaust gases from an engine 206. The first control unit 200 may be arranged to present by means of the said communication communication unit 285 a result of whether the said sensor 235, 245, 255, 265 is defective or not.

A second contro! unit 210 is arranged for communication with the first control unit 200 over a link L210. The second control unit 210 may be connected to the first contro! unit. 200 in a manner that allows it to be removed. The second contro! unit 210 may be a control unit that is external to the vehicle 100. The second contro! unit 210 may be arranged to carry out the method steps according to the invention according to the invention. The second control unit 210 may be used to transfer program code to the first contro! unit 200, in particular, program code to carry out the method according to the invention. Alternatively, the second control unit 210 may be arranged for communication with the first control unit 200 over an interna! network in the vehicle. The second contro! unit 210 may be arranged to carry out essentially the same functions as the first control unit 200, such as, for example, to determine the function of a sensor 235, 245, 255, 265 arranged to determine the level of a component in the exhaust gases from an engine. The second control unit 210 may be arranged, for example, to determine a level of the said component in the said reference gas by means of the said sensor 235, 245, 255, 265. The second control unit 210 may be arranged to compare the level determined in this way with the said known level with respect to the said component and to assess the said function on the basis of the result of the said comparison.

With reference to Figure 2b, there is shown an arrangement according to one design of the present invention. The sensor 235, 245, 255, 265 is connected to the first control unit 200 such that it transfers signals in the same manner as during conventional use of the sensor. According to this design given as an example, the sensor is arranged external to the said exhaust gas passage 290. A measurement housing 275 is connected with the sensor 235, 245, 255, 265 such that it can be removed. The said measurement housing 275 is adapted to be connected to the said sensor 235, 245, 255, 265 in a suitable manner. According to one design given as an example, the said measurement housing 275 can be connected to the said sensor 235, 245, 255, 265 by a threaded joint. According to one design given as an example, the said measurement housing 275 can be connected with the said sensor 235, 245, 255, 265 through snap hooks, through a snap-in function or through another appropriate lock mechanism. The measurement housing 275 is connected through a line 277 to an external source 276 of gas. The external source 276 of gas contains the said reference gas with a known level of the said component, where the said reference gas is under pressure. The flow of reference gas from the external source 276 of gas to the measurement housing 275 can be regulated by a valve 279. The said valve arrangement 279 can be regulated by an appropriate control system, for example, by the first control unit 200, or alternatively manually, using a knob or other appropriate control means. The said valve arrangement 279 is opened for a certain predetermined period of time during measurement, for example, a period of time between 1 and 5 minutes. Since the said reference gas is under pressure in the external source 276 of gas, the said reference gas is expelled by pressure from the said source 276 of gas through the line 277 to the measurement housing 275, In order to ensure that the said reference gas surrounds the said sensor 235, 245, 255, 265 an opening has been arranged in the said measurement housing 275. The reference gas thus flows, during the said measurement, from the external source 276 of gas to the measurement housing 275 and subsequently out of the measurement housing 275 through the said opening. Since the measurement housing 275 surrounds the said sensor 235, 245, 255, 265, the said reference gas will surround the said sensor 235, 245, 255, 265 during the said measurement and will ensure that the level of the said component in the said reference gas is detected. The said sensor 235, 245, 255, 265 detects a level of the said component and transmits signals that contain information about the level HmeasNox, HmeasOx of the said component detected to the first control unit 200. The control unit 200 is in this way arranged to compare the said detected levels with the known levels Ref 1 Nox, Ref 1 Ox, Ref 2 Nox, Ref 2 Ox in the relevant reference gas, and can determine on the basis of this comparison whether the said sensor 235, 245, 255, 265 is defective or not.

According to one embodiment, the reference gas flows out from the said measurement housing 275 to the surrounding air. According to one embodiment, the reference gas flows out from the said measurement housing 275 to a vessel (not shown in the drawings) arranged to withdraw by suction and receive the said reference gas.

With reference to Figure 2c, there is shown an arrangement according to one design of the present invention. The arrangement in Figure 2c differs from the arrangement described in Figure 2b in that a further external reference source 276b of gas is connected to the measurement housing 275. A reference source 276a of gas is in this way connected to the said measurement housing 275 in a manner that allows flow through a line 277a that includes a valve arrangement 279. The said further reference source 276b of gas is in this way connected to the said measurement housing 275 in a manner that allows flow through a line 277b that includes a valve arrangement 279, According to this embodiment, the said sensor 235, 245, 255, 265 can be exposed to two reference gases by controlling the valves 279 for the relevant external source 276a, 276b of gas, without changing the connections of the arrangement. The external sources 276a, 276b of gas contain the said reference gases with different known levels of the said component. During measurement, a first reference gas is supplied at a first timepoint from the first external source 276a of gas into the measurement housing 275 during a certain predetermined period of time, for example, 2 minutes. The said sensor 235, 245, 255, 265 detects a level of the said component and transmits signals that contain information about the level of the said component detected to the first control unit 200. A second reference gas is supplied at a second timepoint from a second external source 276b of gas into the measurement housing 275 during a certain predetermined period of time, for example, 2 minutes. The said sensor 235, 245, 255, 265 detects a level of the said component and transmits signals that contain information about the level of the said component detected to the first control unit 200. The control unit 200 is in this way arranged to compare the said detected levels of the said component with the known levels of the said component in the relevant first and second reference gases, and can determine on the basis of this comparison whether the said sensor 235, 245, 255, 265 is defective or not.

According to one design, the relevant source of reference gas may be connected with an associated measurement housing 275 in a manner that allows flow through a line intended for this. A measurement housing 275 is in this way obtained for each source of reference gas.

With reference to Figure 2d, there is shown an arrangement according to one design of the present invention. The said sensor 235, 245, 255, 265 is connected to the first control unit 200 at the said engine 206 such that it transfers signals in the same manner as during conventional use of the sensor. According to this embodiment, the sensor is arranged at its conventional location at the exhaust gas passage 290. A first external source 276 of gas that contains a first reference gas with a known level of the said component is connected to the said exhaust gas passage 290 through a line 277. The said line 277 may include a valve arrangement 279. According to one embodiment, several external sources of gas that contain reference gases with different known levels of the said components may be connected at the said exhaust gas passage 290. A valve is opened during measurement such that the said reference gas flows from the external source 276 of gas into the said exhaust gas passage 290 during a certain predetermined period of time, for example 3 minutes. The said sensor 235, 245, 255, 265 detects a level of the said component and transmits signals that contain information about the level of the said component detected to the control unit 200. According to one embodiment, a second reference gas may be introduced at a second timepoint into the exhaust gas passage 290 from a second external source of gas (not shown in the drawings) during a certain predetermined period of time. The said sensor 235, 245, 255, 265 detects a level of the said component and transmits signals that contain information about the level of the said component detected to the control unit. The control unit compares the said detected levels with the known levels of the first and second reference gases, respectively, and can determine with the aid of this comparison the function of the said sensor 235, 245, 255, 265.

With reference to Figure 2e, there is shown a holder 295 arranged to hold the said sensor 235, 245, 255, 265 during measurement of the said component of the said reference gas when the said sensor 235, 245, 255, 265 is arranged external to the said exhaust gas passage 290. The said holder 295 may be arranged in a manner that allows it to be removed in an opening in the said exhaust gas passage 290, where the said sensor 235, 245, 255, 265 is located at its conventional location in the said exhaust gas passage 290. The said opening may be arranged, according to one embodiment, to hold the said sensor 235, 245, 255, 265 when the said sensor is located at its conventional location in the said exhaust gas passage 290. The said holder 295 may be arranged in a manner that allows it to be removed at the said opening in an appropriate manner, for example, by means of threads. The holder 295 may include two flexible holders in order to provide simple application of the sensor 235, 245, 255, 265 and simple removal of the sensor. The holder may be constituted by an appropriate material, for example steel, or another appropriate metal alloy or plastic.

With reference to Figure 2f, the said sensor 235, 245, 255, 265 is there shown arranged in the said holder 295 in a manner that allows it to be removed.

With reference to Figure 3a, there is shown a diagram according to one design of the present invention in which the said sensor is a NOx sensor. The measured level of NOx, HmeasNox, is shown in Figure 3 as a function of the level of NOx in the reference gas. The levels of NOx are specified in units of ppm (parts per million). According to one design of the present invention, at least two measurements are carried out with respect to at least two reference gases, Ref 1 NOx, Ref 2 NOx. The said level of reference gas NOx can be chosen in a suitable manner such that the complete range of measurement of the sensor is covered. According to one example, a gas comprising a NOx level of 900 ppm can be used as reference gas. According to one example, a second reference gas can consist of air, in which the said level of IMQx is 0 ppm.

According to one aspect of the present invention, an interval can be determined within which the said IMOx sensor can be regarded as being correct. The said interval may differ, depending on the said level of NOx in the said reference gas. According to one example, the said interval can be +/-10 ppm when the said reference gas contains 900 ppm NOx. According to one example, the said interval can be +/-5 ppm when the said reference gas contains 0 ppm NOx. The said interval can be determined also depending on how accurately the said level of reference gas is measured. According to one aspect of the invention, the sensor 255, 265, is considered to be defective when the sensor detects a level of MOx HmeasNox that lies outside of the said interval. Measured values from a first second 255, Sensor 1, and from a second sensor 265, Sensor 2, are shown in Figure 3a. According to this embodiment, two reference gases, with a first known level of NOx, Ref 1 MOx, and a second known level NOx, Ref 2 NOx, have been used. Sensor 1 shows the measured values for the relevant reference gas, which values are located within a predetermined interval for the relevant reference gas. Sensor 2 shows the measured values for the relevant reference gas, which values lie outside of a predetermined interval. It can therefore be concluded that the function of Sensor 1 is correct and that the function of Sensor 2 is erroneous and defective. According to one design of the present invention, only one reference gas is used to determine the function of a NOx sensor. According to a second design, at least two reference gases are used to determine the function of a NOx sensor.

According to one aspect of the invention, the said measurements are carried out when the IMOx sensor 255, 265 is arranged at its conventional location at the exhaust gas passage 290.

According to one aspect of the invention, the said measurements are carried out when the NOx sensor 255, 265 is arranged external to the said exhaust gas passage 290.

With reference to Figure 3b, there is shown a diagram according to one design of the present invention in which the said sensor 235, 245 is a lambda sensor. The measured level of oxygen HmeasOx is shown in Figure 3b along the y-axis and the level of oxygen in the reference gas is shown along the x-axis. The level of oxygen is specified as a percentage [%]. According to one design of the said invention, at least two measurements are carried out for at least two reference gases, Ref 1 Ox, Ref 2 Ox. The level of oxygen in the reference gas can be chosen in a suitable manner such that the complete range of measurement of the sensor is covered. According to one example, a reference gas can consist of 100% nitrogen. According to one example, a reference gas can consist of 79% nitrogen and 21% oxygen. According to one example, a reference gas can consist of 99% nitrogen and 1% oxygen. According to one example, a reference gas can consist of 99.5% nitrogen and 0.5% oxygen. According to one example, the said reference gas can consist of up to 21% oxygen.

According to one aspect of the present invention, an interval can be determined, within which a level of oxygen detected by the said lambda sensor is to lie in order for the said lambda sensor to be considered to be correct. The said interval can be chosen depending on the said level of oxygen in the said reference gas. According to one example, the said interval can be +/-Q.5% when the said reference gas contains 21% oxygen. According to one example, the said interval can be +/-0.1% when the said reference gas contains 21% oxygen. The said interval can be selected also depending on how accurately the said level of reference gas is measured. According to one aspect of the invention, the sensor is considered to be defective when the sensor detects a level of oxygen HmeasOx that lies outside of the said predetermined interval. Measured values from a first second 235, Sensor 1, and from a second sensor 245, Sensor 2, are shown in Figure 3b. According to this embodiment, two reference gases, with a first known level of oxygen, Ref 1 Ox, and a second known level oxygen, Ref 2 Ox, have been used. Sensor 1 shows the measured values for the relevant reference gas, which values are located within a predetermined interval for the relevant reference gas. Sensor 2 shows the measured values for the relevant reference gas, which values lie outside of a predetermined interval. It can therefore be concluded that the function of Sensor 1 is correct and that the function of Sensor 2 is defective. According to one design of the present invention, only one reference gas is used to determine the function of a lambda sensor. According to a second design, at least two reference gases are used to determine the function of a lambda sensor. According to one aspect of the invention, the said measurements are carried out when the said lambda sensor 235, 245 is arranged at its conventional location at the exhaust gas passage 290.

According to one aspect of the invention, the said measurements are carried out when the said lambda sensor 235, 245 is arranged external to the said exhaust gas passage 290.

Figure 4a illustrates schematically a flow diagram of a method to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine. The method comprises a first method step s401. The step s401 comprises the following steps:

- to expose the said sensor to a reference gas, other than the said exhaust gases, with a known level of the said component;

- to determine a level of the said component in the said reference gas by means of the said sensor;

- to compare the level determined in this way with the said known level with respect to the said component; and

- to assess the said function on the basis of the result of the said comparison.

The method is terminated after the step s401.

Figure 4b illustrates schematically a flow diagram of a part of a method to determine the function of a sensor 235, 245, 255, 265 arranged to determine the level of a component in the exhaust gases from an engine 206, according to one aspect of the present invention.

The method includes a first method step s410. The method step s410 can include the step of activating the method according to the invention. The said activation can be carried out by an operator at the vehicle 100. The said activation can carried out by workshop personnel or service personnel at a workshop or service facility. The said activation can take place by means of at least one of the said presentation means 280 and the said communication unit 285.

The method step s410 can include the step of arranging the said sensor 235, 245, 255, 265 external to the said exhaust gas passage 290. When the sensor 235, 245, 255, 265 is arranged external to the said exhaust gas passage 290, a measurement housing 275 is connected to the said sensor. The said measurement housing 275 is connected to an external source 276 of gas in which a reference gas is contained. According to one example, the said sensor 235, 245, 255, 265 can be arranged externa! to the said exhaust gas passage 290 in a holder 295. The said holder 295 can be arranged, according to one example, in the opening in which the said sensor 235, 245, 255, 265 is arranged, during conventional use of the said sensor.

The method step S410 can include the step of connecting an external source 276 of gas, in which a reference gas is contained, to the said exhaust gas passage 290. According to this embodiment, the sensor 235, 245, 255, 265 is retained located at its conventional location.

The method step s410 may include the step of achieving predetermined operating conditions, in the form of, for example, a particular lowest temperature at the said sensor 235, 245, 255, 265. This temperature can be controlled by the control system 200 of the engine.

After the method step s410, a subsequent method step s420 is carried out.

The method step s420 includes the step of exposing the said sensor 235, 245, 255, 265 to a first reference gas. The said first reference gas has a known level Ref 1 Mox, Ref 1 Ox of one component. The method step s420 can include the step of allowing the said reference gas to flow in an appropriate manner, with the aid of an excess pressure, at the said sensor during a certain predetermined period of time, for example 2 minutes. This period of time is selected in order to ensure that the sensor is fully surrounded by the said reference gas. After the method step s420, a subsequent method step s430 is carried out.

The method step s430 can include the step of determining, with the aid of the sensor 235, 245, 255, 265, a level HmeasNox, HmeasOx of the said component in the said first reference gas.

After the method step s43G, a subsequent method step s440 is carried out.

The method step s440 can include the step of comparing the level HmeasNox, HmeasOx that has been determined with the known level Ref 1 Nox, Ref 1 Ox of the said first reference gas with respect to the said component. The comparison can be carried out by a suitable unit at the control system of the engine, for example the first control unit 200 or the second control unit 210, or by the said communication unit 285. When the level HmeasNox, HmeasOx that has been determined lies within a certain predetermined interval that surrounds the known level Ref 1 Nox, Ref 1 Ox of the said component, it can be concluded and determined that the sensor 235, 245, 255, 265 is correct. When the level that has been determined lies outside of a certain predetermined interval that surrounds the known level of the said component, it can be concluded and determined that the sensor is defective. After the method step s440, a subsequent method step s450 is carried out.

The method step s450 can include the step of exposing the said sensor 235, 245, 255, 265 to a second reference gas. The said second reference gas has a known level Ref 2 Nox, Ref 2 Ox of one component. The method step s450 can include the step of allowing the said reference gas to flow in an appropriate manner, with the aid of an excess pressure, at the said sensor during a certain predetermined period of time, for example 2 minutes. This period of time is selected in order to ensure that the sensor is fully surrounded by the said reference gas. After the method step s450, a subsequent method step s460 is carried out.

The method step s460 can include the step of determining, with the aid of the sensor 235, 245, 255, 265, a level HmeasNox, HmeasOx of the said component in the said second reference gas.

After the method step s460, a subsequent method step s470 is carried out.

The method step s470 can include the step of comparing the level HmeasNox, HmeasOx that has been determined with the known level Ref 2 Nox, Ref 2 Ox of the said second reference gas with respect to the said component. The comparison can be carried out by, for example, the first control unit 200 or by the said communication unit 285. When the level HmeasNox, HmeasOx that has been determined lies within a certain predetermined interval that surrounds the known level Ref 21 Nox, Ref 2 Ox of the said component, it can be concluded that the sensor is correct. When the level that has been determined lies outside of a certain predetermined interval that surrounds the known level of the said component, it can be concluded that the sensor is defective. it should be pointed out that the level HmeasNox that has been determined is compared in this way with the known levels Ref 1 Nox and Ref 2 Nox, respectively, it should be pointed out that the level HmeasOx that has been determined is compared in this way with the known levels Ref 1 Ox and Ref 2 Ox, respectively.

The method is terminated after the method step s470. With reference to Figure 5, there is shown a drawing of a design of an arrangement 500. The control units 200 and 210 that are described with reference to, for example, Figure 2a may, in one design, comprise the arrangement 500, The arrangement 500 comprises a non-transient memory 520, a data processing unit 510 and a read/write memory 550. The non-transient memory 520 has a first section of memory 530 in which a computer program, such as an operating system, is stored in order to control the function of the arrangement 500. Furthermore, the arrangement 500 comprises a bus controller, a serial communication port, I/O means, an A/D converter, a unit for the input and transfer of time and date, an event counter and an interrupt controller (not shown in the drawing). The non- transient memory 520 has also a second section of memory 540.

A computer program P is provided that can comprise routines to determine the function of a sensor arranged to determine the level of a component in exhaust gases from an engine.

The computer program P can comprise routines to control the exposure of the said sensor 235, 245, 255, 265 to a reference gas, other than the said exhaust gases, with a known level of the said component. The computer program P can comprise routines to determine a level of the said component in the said reference gas by means of the said sensor 235, 245, 255, 265. The computer program P can comprise routines to compare the level determined in this way with the said known Ievei with respect to the said component. The computer program P can comprise routines to assess the said function on the basis of the result of the said comparison.

The computer program P can comprise routines to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine 206, whereby the said sensor is a NOx sensor or a lambda sensor. The computer program P can comprise routines to control the exposure of the said sensor 235, 245, 255, 265 to a first reference gas with a known level of the said component. The computer program P can comprise routines to control the exposure of the said sensor 235, 245, 255, 265 to at least one further reference gas, where the said further reference gas has a level of the said component that differs from the level in the said first reference gas.

The computer program P can comprise routines to control the exposure of the said sensor 235, 245, 255, 265 to a first reference gas with a known level of the said component. The computer program P can comprise routines to control the exposure of the said sensor to at least one further reference gas, where the said further reference gas has a level of the said component that differs from the level in the said first reference gas, whereby the said different, known levels are selected for the coverage of the range of measurement of the sensor 235, 245, 255, 265.

The computer program P can comprise routines to consider, during the determination of the said function of a sensor 235, 245, 255, 265 arranged to determine the level of a component in the exhaust gases from an engine 206, signals from the said sensor that is retained connected to, for example, the first control unit such that it transfers signals, in the same manner as during the conventional use of the sensor 235, 245, 255, 265.

The computer program P can comprise routines where, during the determination of the said function of a sensor 235, 245, 255, 265 arranged to determine the level of a component in the exhaust gases from an engine 206, the said exposure of the reference gas is carried out with the said sensor 235, 245, 255, 265 arranged at its conventional location at the exhaust gas passage 290 or arranged external to the said exhaust gas passage 290. The computer program P can comprise routines where, during the determination of the said function of a sensor 235, 245, 255, 265 arranged to determine the level of a component in the exhaust gases from an engine 206, one reference gas is constituted by air.

The program P may be stored in an executable form or in a compressed form in at least one of a memory 560 and a read/write memory 550.

When it is described that the data processing unit 510 carries out a certain function, it is to be understood that the data processing unit 510 carries out a certain part of the program that is stored in the memory 560, or a certain part of the program that is stored in the read/write memory 550.

The data processing arrangement 510 can communicate with a data port 599 through a data bus 515. The non -transient memory 520 is intended for communication with the data processing unit 510 through a data bus 512. The separate memory 560 is intended to communicate with the data processing unit 510 through a data bus 511. The read/write memory 550 is arranged to communicate with the data processing unit 510 through a data bus 514. The links L210, L230, L250, L255, L265, L280 and L285 can, for example, be connected to the data port 599 (see Figure 2a).

When data is received at the data port 599 it is temporarily stored in the second section of memory 540. When the data that has been received has been temporarily stored, the data processing unit 510 is prepared for the execution of code in a manner that has been described above. According to one design, the signals received at the data port 599 comprise information about the IMO _x level determined by the relevant IMOx sensor 255, 265. According to one design, the signals received at the data port 599 comprise information about the oxygen level determined by the relevant lambda sensor 235, 245. The signals received at the data port 599 can be used by the arrangement 500 to determine the function of a sensor arranged to determine the level of a component in the exhaust gases from an engine. Parts of the methods described here may be carried out by the arrangement 500 with the aid of the data processing unit 510, which runs the program stored in the memory 560 or in the read/write memory 550. When the arrangement 500 runs the program, the method described here is executed.

The previous description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description of the invention. It is not intended to be exhaustive or to limit the invention to the variants that have been described. Many modifications and variations will be obvious for one skilled in the arts. The embodiments were selected and described in order to best explain the principles of the invention and its practical applications, and thus to make it possible for those skilled in the arts to understand the invention for various embodiments and with the various modifications that are appropriate for the intended use.