[amidgeha]

Evaporative Emission System Incorrect Purge Flow

The Engine Control Module (ECM) tests the Evaporative Emission (EVAP) system for the following conditions:

- Large and small leaks

- Excess vacuum

- Purge flow during non-commanded conditions

- Fuel Level and Fuel Pressure sensor faults

- EVAP Purge and Vent Valve faults

The ECM monitors the Fuel Tank Pressure sensor in order to determine the level of vacuum/pressure in the EVAP system. The ECM commands both the EVAP Purge Solenoid and the EVAP Vent Valve ON when the conditions are met in order to apply an engine vacuum to the EVAP system. The ECM commands the EVAP Purge Solenoid OFF once the system has reached a predetermined level of vacuum. This test verifies if a vacuum can be achieved in the EVAP system. Failure to develop a vacuum may be caused by a large leak or a restriction.

Cause:
Missing Fuel cap
Incorrect fuel filler cap used
Fuel filler cap remains open or fails to close
Foreign matter caught in fuel filler cap
Incorrect fuel tank vacuum relief valve

Symptoms:
Check engine light
Possible a noticeable fuel odor caused by the release of fuel vapors