| 摘要 |
Provided is a method for diagnosing an EGR system. To this end, the present invention includes: a setting step of setting an ignition time map according to EGR efficiency when an EGR system operates normally; a studying step of dividing an output value reflecting the driving state of a vehicle into an operation area where the EGR system operates and a non-operation area where the EGR system does not operate and studying and storing a recognition amount of ignition time by a knocking generation in each area; an extracting step of extracting a correction amount of ignition time which is caused only by the effect of an operation of the EGR system by using a difference between the recognition amount of ignition time studied in the operation area and the recognition amount of ignition time studied in the non-operation area when a knocking occurs in the operation area; and a measuring step of measuring a change amount of EGR efficiency caused by the effect of an operation of the EGR system by measuring the EGR efficiency for the correction amount of ignition time by applying the correction amount of ignition time to the ignition time map. The measuring step more includes a determining step of determining whether the correction reason of ignition time is a failure of an EGR rate or a failure of an EGR cooler by using a difference between the temperature of fresh air measured in the front end of an inhalation line and the temperature of gas in which EGR gas and fresh air measured in the rear end of the inhalation line are mixed. |
