| 摘要 |
PROBLEM TO BE SOLVED: To accurately diagnose the response characteristic of an air-fuel ratio sensor without affecting the behavior of an internal combustion engine.SOLUTION: An air-fuel ratio sensor 420 is provided in the exhaust passage of an engine 10. An ECU 200 executes response diagnosis of the air-fuel ratio sensor 420 on the basis of the output voltage of the air-fuel ratio sensor 420 at the time when exhaust is detected in a period during which the engine 10 rotates in the stop state of fuel injection. Concretely, the ECU 200 diagnoses whether change of the output voltage of the air-fuel ratio sensor 420 catches the behavior that an air-fuel ratio abruptly changes in a lean direction in the period. |
