Patent ID: 6752011
Filing Date: 2004-06-22
Classification: F01P,F02D,Y02T

Abstract:
A thermostat failure diagnosis apparatus for an internal combustion engine, which diagnoses a failure of a thermostat provided in a cooling water passage of the internal combustion engine, comprising:cooling water temperature detection means for detecting a cooling water temperature of an internal combustion engine at an upstream side of the thermostat; detection means for detecting one of an actual fuel injection quantity of the internal combustion engine and a parameter indicative of the actual fuel injection quantity; diagnosis means for detecting, only when one of the detected actual fuel injection quantity and the detected parameter is equal to or higher than a first predetermined value, the failure of the thermostat on the basis of at least one of a time in which an increasing amount of the cooling water temperature reaches a second predetermined value and a time in which the cooling water temperature rises to a third predetermined temperature, after starting of the internal combustion engine; and a timer that counts a period of time where said one of the detected actual fuel injection quantity and the detected parameter is lower than the first predetermined value, such that the failure of the thermostat detection is terminated when the counted period of time exceeds a fourth predetermined value.