Thermostat fault diagnosis system for the cooling system of a motor vehicle engine

摘要

PROBLEM TO BE SOLVED: To enable to judge thermostat failure more precisely irrespective of the extent of temperature rise of cooling water. ;SOLUTION: With this diagnosis device, anticipated temperature θ e-p of cooling water for engine 1 based on engine-operation parameter such as engine load, etc., is calculated. Actual temperature θ ea of cooling water is detected with water temperature sensor S1. Radiation volume Q orh from radiator 3 is calculated based on the aggregate of values given from deviation of θ ea deducted from θ ep multiplied by car velocity Vs and current deviation value of θ ea deducted from θ ep. On the other hand, heat-intake volume Q ig of cooling water from engine 1 is calculated based on engine operation parameter such as engine load. Ratio of radiation Q orh to heat-intake volume Q ig is calculated as heat volume ratio R. If heat volume ratio R is greater than the judged threshold α1 when anticipated temperature θ ep reaches around specified valve-opening temperature of thermostat 5, it is judged that as valve-opening failure due to excessive radiation from radiator 3 leaving thermostat 5 open.;COPYRIGHT: (C)2001,JPO