| 摘要 |
A secondary air supply system includes a passage, which supplies the exhaust system of an internal engine with secondary air, an air pump, which supplies secondary air to the exhaust system through the passage, and a valve, which opens and closes the passage. The exhaust system includes an air-fuel ratio sensor for providing information on which abnormality tests are based. In a testing procedure, the air-fuel ratio is monitored under various conditions of the air pump and the value to determine whether the valve has failed to open or close and whether the pump has failed to start or stop.
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