Patent ID: 6725710
Filing Date: 2004-04-27
Classification: F01P,F02D,G01K,Y02T

Abstract:
A method for diagnosing an open-malfunction of a thermostat of an internal combustion engine upon start of the engine, comprising the steps of:a) measuring a coolant temperature of a coolant on an engine side of the thermostat; b) determining an accumulated value of quantity of heat generated by the engine since engine start; c) comparing a starting time coolant temperature measured upon starting the engine with a predetermined temperature which is set to be lower than an opening temperature of the thermostat; d) comparing the accumulated value of quantity of heat with a predetermined quantity of heat generated by the engine; and e) diagnosing whether the thermostat has an open-malfunction based on the engine side coolant temperature, when the starting time coolant temperature is lower than the opening temperature of the thermostat and the accumulated value of quantity of heat has reached a predetermined quantity.