| 摘要 |
A method of detecting failure in a secondary air supply system for an internal combustion engine comprises the steps of (1) causing the secondary air supply system to operate when the engine is in a predetermined decelerating condition, (2) detecting a first value of concentration of an exhaust gas ingredient, from an output from a first exhaust gas ingredient concentration sensor arranged in the exhaust passage at a location upstream of the secondary air supply system when the engine is in the predetermined decelerating condition, (3) detecting a second value of concentration of the exhaust gas ingredient, from an output from a second exhaust gas ingredient concentration sensor arranged in the exhaust passage at a location downstream of the secondary air supply system when the engine is in the predetermined decelerating condition, (4) determining whether or not the first value of concentration of the exhaust gas ingredient is lower than a first predetermined value, (5) determining whether or not the second value of concentration of the exhaust gas ingredient is lower than the first predetermined value, and (6) determining that there is failure in the secondary air supply system when it is determined that the first and second values of concentration of the exhaust gas ingredient are both lower than the first predetermined value.
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