Patent ID: 7299993

Claim:
An apparatus for detecting a failure of a thermostat provided between an engine and a radiator, the thermostat regulating circulation of cooling water between the engine and the radiator, the apparatus comprising: a first temperature sensor provided on a radiator side relative to the thermostat; a second temperature sensor provided on an engine side relative to the thermostat; and a controller configured to: determine that the engine has reached a desired warm condition if a temperature detected by the second temperature sensor reaches a first predetermined value; perform a failure detection process if it is determined that the engine has reached the desired warm condition, the process detecting a failure of the thermostat based on an amount of change in a temperature detected by the first temperature sensor, without using a temperature detected by the second temperature sensor; and determine that the engine has reached the desired warm condition if an amount of change in the temperature detected by the second temperature sensor exceeds a second predetermined value before the temperature detected by the second temperature sensor reaches the first predetermined value.