Patent ID: 6532808
Filing Date: 2003-03-18
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 the internal combustion engine at an upstream side of the thermostat; parameter detection means for detecting a control parameter of the internal combustion engine; outside air temperature detection means for detecting one of an outside air temperature and a parameter related to the outside temperature; and diagnosis means for detecting 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 first predetermined value and a time in which the cooling water temperature rises to a second predetermined value, in a case where a control parameter value detected by the parameter detection means is equal to or higher than a third predetermined value after starting of the internal combustion engine, the diagnosis means stops the failure diagnosis when, at the time of engine start, the cooling water temperature detected by the cooling water temperature detection means is equal to or higher than the detected outside air temperature, and the detected water temperature does not rise to an opening/closing switching temperature of the thermostat within a predetermined time after the engine start.