| 摘要 |
PROBLEM TO BE SOLVED: To accurately examine whether there is a normally ON abnormality in which an air pump is kept continuously operated, and reduce a computational load on a control device, in a secondary air supply system having an air pump for supplying secondary air to an exhaust pipe of an engine. SOLUTION: A comparison between a pressure (air-pump-operated pressure) P1 in a secondary air line detected by a pressure sensor during the operation control of the air pump and a pressure (air-pump-stopped pressure) P2 in the secondary air line detected by the pressure sensor after the stop of the operation control of the air pump determines whether there is an abnormality in the air pump. This can accurately determine whether there is a normally ON abnormality in the air pump regardless of variations in the internal pressure of the secondary air line due to performance variations in the air pump, dimensional variations in the secondary air line, and the like. This can also dispense with the need to compute pressure behavior patterns during and after air pump operation to simplify abnormality diagnostic processing and reduce a computational load on the control device. COPYRIGHT: (C)2008,JPO&INPIT
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