Evaporative Purge System Monitoring

Monitoring Structure

General Description

The purge flow from the charcoal canister through the purge valve is monitored after fuel system adaption is completed and the lambda controller is at closed loop condition. The diagnosis is started 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 Jean shift.
After this procedure the diagnosis is completed and the evaporative purge system resumes working normally.

Step 2 - For a stoichiometric mixture

In this case the lambda controller does not need to compensate for a deviation. Therefore, after finishing the regular purging, the purge valve is opened and closed abruptly several times. The effect of additional cylinder charge triggers by a variation of the engine idle speed.
A predetermined value is reached if the system functions properly and the diagnosis procedure is completed.