Internal combustion engine failure diagnosis method and internal combustion engine failure diagnosis device

摘要

PPROBLEM TO BE SOLVED: To diagnose the presence of an exhaust gas leakage from a passage selector valve 5. PSOLUTION: A main passage through which exhaust gas flows in normal operation is composed of an upstream main passage 3, a downstream main passage 8 and a main catalytic converter 9. A by-pass passage branches off from the upstream main passage 3. When the passage selector valve 5 is put in a closed state to close the upstream main passage 3, the temperature of exhaust gas exhausted from a cylinder is temporarily changed to diagnose whether there is a leakage in the passage selector valve 5 from the temperature change in the upstream main passage 3. When exhaust gas leaks downstream from the passage selector valve 5, high-temperature exhaust gas exhausted from the cylinder flows into the upstream main passage 3, and the internal temperature of the upstream main passage 3 rises. The exhaust gas leakage from the passage selector valve 5 can be positively detected from the internal temperature change of the upstream main passage 3. PCOPYRIGHT: (C)2008,JPO&INPIT