PURPOSE: To reduce electric power consumption and to prevent the early deterioration of a heating element by stopping the supply of electric current when the low-temp. condition of an engine is detected.
CONSTITUTION: The engine speed is detected from the output signal of a revolving speed sensor 28 and is compared with the prescribed high revolving speed in an air-fuel ratio control circuit 32. Whether the cooling water temp. outputted from a cooling water temp. sensor 29 is the prescribed low temp. or not is discriminated by the circuit 32 when the detected speed is below the prescribed high revolving speed. The current supply from a heater current supply circuit 36 to an oxygen concn. sensor 30 is stopped by the heater current supply stop command of the circuit 32 when the low-temp. condition of the engine 21 is detected. The engine 21 is in the low-temp. state until the warming up thereof is completed and since this state continues relatively long, the electric power consumption of the power source is reduced and the early deterioration of the heating element is stopped by stopping the supply of the current to the heating element.
KUSHIDA NORITAKA
KAWANABE TOMOHIKO
HASEBE HIROSHI
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