| 摘要 |
PROBLEM TO BE SOLVED: To provide a thermostat diagnosis device capable of accurately diagnosing operation status of a thermostat provided in a cooling water passage of an internal combustion engine. SOLUTION: The diagnosis device for diagnosing operation status of the thermostat provided in the cooling water passage of the internal combustion engine estimates transition of cooling water temperature under conditions that normal operation of the thermostat is assumed. Then, a simulated counter correction value K is calculated based on lubrication oil temperature estimated from the pre-trip water temperature TW, the intake air temperature THA, the soak time ST, and the pre-operating time DT for correcting the estimated cooling water temperature so as to consider the effect of the lubrication oil of the internal combustion engine on the cooling water temperature. When the actual rising rate of cooling water temperature transition is lower than the estimated rising rate of the temperature transition, the device diagnoses that the thermostat has abnormalities. COPYRIGHT: (C)2004,JPO&NCIPI
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