| 摘要 |
PROBLEM TO BE SOLVED: To diagnose for the closing of one side of a branch passage of a secondary air supply passage. SOLUTION: In this secondary air supply device, the branch passage branched from the secondary air supply passage supplying a secondary air communicates with the discharge passage of each of the banks of a V-internal combustion engine. A secondary air flow QAI supplied to the discharge passage is detected on the upstream side of a branch position in the secondary air supply passage (S3). Based on the pulsation frequency characteristic of the secondary air on the basis of the secondary air flow QAI, the branch passage is diagnosed for the closing of one side thereof (S6, S8, S10). For example, the pulsation amplitude of the secondary air according to the pulsation frequency is calculated based on the secondary air flow QAI (S4), and compared with a predetermined value in a predetermined pulsation frequency x. When the pulsation amplitude is equal to or less than a predetermined value, the diagnosing device determines that one side of the branch passage of the secondary air supply passage is closed (S10). COPYRIGHT: (C)2007,JPO&INPIT
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