Test Group VBM4.4JGKEK & VBM5.4V8GFEK

Evaporative Purge System Monitoring General Description -  Purge flow from the charcoal canister through the purge valve is monitored after fuel system adaptation is completed and the lambda controller is at closed loop condition. See Figure. The diagnosis is started during one of two steps during regular purging.

• Step 1 (For Rich Or Lean Mixture) -  Flow through the purge valve is assumed as soon as the lambda controller is compensating for a rich or a lean shift. After this procedure the diagnosis is completed, and the evaporative purge system resumes working normally.
• Step 2 (For Stoichiometric Mixture) -  In this case the lambda controller does not need to compensate for a deviation. Therefore, after finishing the regular purging operation, the purge valve is opened and closed abruptly several times. The effect of additional cylinder charge, triggers a variation of engine idle speed. If a predetermined value is reached, the diagnosis procedure is completed.