| 摘要 |
<p>PROBLEM TO BE SOLVED: To accurately determine whether a fault occurs in a water temperature sensor for an internal combustion engine or not. SOLUTION: A control circuit 30 for an internal combustion engine receives the output of a water temperature sensor 10 and also engine-operational parameters which affect the rising speed of the temperature of cooling water after the start-up of the engine from an air flow meter 21, an intake-air temperature sensor 23, a heater-blower air-quantity setting switch 27 and the like. The control circuit 30 calculates a counter increment on the basis of these parameters and increases the value of a warm-up counter WCT by the calculated increment every predetermined period. The value of the warm-up counter thus increases corresponding to the actual rising speed of the temperature of cooling water. When the value of the warm-up counter reaches a predetermined reference temperature, if the indicated value of the water temperature sensor falls below the reference temperature, the control circuit determines that an abnormality occurs in the water temperature sensor. The value of the warm-up counter which increases corresponding to the actual rise of the temperature of cooling water thus determines the timing of fault diagnosis, which allows accurate fault diagnosis.</p> |
