FAILURE DIAGNOSTIC DEVICE FOR HYBRID VEHICLE

摘要

PROBLEM TO BE SOLVED: To provide a failure diagnostic device for a hybrid vehicle, which can accurately and easily judge the diagnosis of the failure of an evaporated fuel recovering system and an exhaust gas purifying catalyst while improving performance of fuel consumption. SOLUTION: In a hybrid vehicle, an evaporated fuel recovering system is arranged which is equipped with a fuel tank 31 and a purge passage 37 communicating the fuel tank 31 with a surge tank 25, negative pressure in the inside of the surge tank 25 is introduced to the evaporated fuel recovering system, and the failure of the evaporated fuel recovering system is diagnosed based on pressure change caused by the introduction of the negative pressure. The deterioration of a three-way catalyst is judged based on a reverse ratio A/B being a ratio of rich reverse frequency A to lean reverse frequency B of upstream and downstream side O2 sensors 28, 29. An engine 1 is basically operated at high efficiency, therefore performance of fuel consumption can be improved, and also the failure of the evaporative fuel recovering system and exhaust gas purifying catalyst can be accurately and easily diagnosed.