| 摘要 |
A method is provided for diagnosing the rationality of a thermostat in a motor vehicle. The method includes an engine warm-up model and a thermostat diagnostic. The engine warm-up model predicts the temperature that the engine coolant temperature should be equal to at a given time after start-up. This is based on the engine coolant temperature at start-up, ambient air temperature, and how the vehicle is driven subsequent to start-up. This predicted engine coolant temperature is compared to the actual engine coolant temperature as read by an engine coolant temperature sensor. The error between the predicted engine coolant temperature and the actual engine coolant temperature is calculated and integrated over time. The thermostat diagnostic runs at a pre-selected time after start-up and compares the integrated error to a calibrated threshold value. Depending upon the results of the comparison, a pass, fail, or inconclusive condition is determined.
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