PURPOSE: To set an appropriate outside air temperature to the condition when an actual outside air temperature is raised during an engine stop.
CONSTITUTION: A deviation ΔT between a memory value Tadm and a detected value Ta is determined when an engine temperature is high and the sensor detected value Ta is larger than the memory value Tadm (when both of each judgment in steps 103 and 105 are NO) in an initial treatment after an engine started (step 106). The rise of an actual outside air temperature is deemed when the deviation ΔT is 10°C or less (in the case of YES in step 107). Reversely, exceeding 10°C (in the case of NO in step 107) is an unnatural temperature rise, accordingly this is regarded as a temperature rise due to the thermal effect of the engine. When the rise of the actual outside air temperature is judged, the increment of the 3/4 time of the deviation ΔT previously determined is added to the memory value Tadm, and the added value is set as an appropriate outside air temperature Tad (step 118).