Patent ID: 6386022
Filing Date: 2002-05-14
Classification: F01P,F02D,G01K,Y02T

Abstract:
A thermostat malfunction detecting system for an internal combustion engine thermostat provided in a coolant circulating path, said system comprising:coolant temperature detecting means in addition to said thermostat for detecting coolant temperature on the coolant circulating path on the engine side from said thermostat; temperature determining means which responds to said temperature detecting means for determining whether the coolant temperature detected upon starting said engine is lower than an opening temperature of said thermostat; open-malfunction diagnosing means for diagnosing, when the coolant temperature detected upon starting said engine is lower than the opening temperature, whether said thermostat has an open-malfunction based on the engine side coolant temperature detected by said coolant temperature detecting means in a temperature range in which said thermostat is normally to be closed; and closure-malfunction diagnosing means for diagnosing whether said thermostat has a closure-malfunction in which said thermostat is kept closed based on the engine side coolant temperature detected by said coolant temperature detecting means in the temperature range in which said thermostat is to normally open.