| 摘要 |
PROBLEM TO BE SOLVED: To diagnose the performance of an intake air volume detector with high accuracy by performing a diagnostic process on the basis of a relation between an intake air variable and a throttle valve opening variable in a stable operation zone. SOLUTION: Judgement is made about whether a change in the opening TVO of a throttle valve 7 detected with a throttle sensor 11 is equal to or above the preset amountΔTVO. When the change is determined as equal to or above the preset amountΔTVO, the variableΔQ of an intake air flow rate detected with an air flow meter 6 is calculated before and after the change of the opening of the valve 7. Also, the variableΔQ is corrected by use of a separately calculated air density correction factor, thereby finding a correction value AFQ. As a result, high diagnostic accuracy can be maintained. The performance of the air flow meter 6 is diagnosed on the basis of the variableΔTOV of the opening of the throttle valve 7 and the correction value AFQ of the intake air flow rate. According to this construction, the performance drop of the air flow meter 6 other than an absolute failure such as a wire breakage can be diagnosed simply by monitoring a value detected with the sensor 11, deepening on an engine operation mode.
|
