Controller of an internal combustion engine for determining a failure of a thermostat

摘要

A controller provided in accordance with the invention determines a failure of a thermostat that opens and closes a passage through which cooling water circulates between a radiator and an engine. The controller prohibits the failure determination if a water temperature of the engine decreases by more than a predetermined amount during a predetermined period from the time when a rotational speed of the engine exceeds a predetermined rotational speed. Thus, when the thermostat opens due to a high rotational speed of the engine, the failure determination is prohibited. Therefore, it is avoided that the thermostat operating normally is judged to be faulty.