Fault diagnosis method, fault diagnosis system, and fault diagnosis device for engine

摘要

In the present fault diagnosis method and the fault diagnosis system for an engine, an external diagnosis device: obtains continuous data on the incidences of misfire by misfiring cylinders from the vehicle's side with regard to the actually occurring misfire or past incidences of misfire; detects a misfire pattern, which is to be classified according to the presence of continuous incidences of misfire, on the basis of the continuous data; and narrows down a fault site in accordance with the misfire pattern.

主权项

1. A fault diagnosing method for diagnosing an engine by tracking down a faulty region in the event of a misfire that occurs in a multicylinder engine having a misfire detecting function, using an external diagnosing machine that communicates with an engine control unit, comprising the steps of:
reading a diagnostic fault code representative of a misfiring cylinder from the engine control unit into the external diagnosing machine; detecting misfire patterns classified depending on whether or not successive misfires occur in the misfiring cylinder; and tracking down faulty regions according to the detected misfire patterns, wherein the step of detecting the misfire patterns further comprises the steps of: idling the engine in accordance with an instruction from the external diagnosing machine in an attempt to repeat a misfire in the misfiring cylinder; if a misfire is repeated in the misfiring cylinder, detecting the repeated misfire pattern; and if a misfire is not repeated in the misfiring cylinder, detecting the misfire pattern based on successive data generated upon occurrence of a misfire in the misfiring cylinder, which are stored in the engine control unit at a time that the diagnostic fault code is generated.