Evaporative Emissions System: Testing and Inspection

EVAP Canister Purge Valve Circuit:

Circuit Description:
Canister purge is controlled by a solenoid that allows vacuum to purge the canister when energized. The PCM supplies a Pulse Width Modulated (PWM) ground to energize the solenoid (purge "ON").

If the DLC diagnostic EVAP request terminal is grounded with the engine stopped or the following is met with the engine running, the purge solenoid is energized (purge "ON").

^ Engine run time after start more than 20 seconds on a warm engine or 2.5 minutes on a cold engine
^ Engine coolant temperature above 60°C (158°F)
^ Intake Air Temperature (IAT) is above 9.5°C (50°F)

EVAP Canister Purge Valve Check:

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if the solenoid is opened or closed. The solenoid is normally de-energized in this step, so it should be closed.

2. Completes functional check. This should normally energize the solenoid and allow vacuum to the gage (purge "ON").

Diagnostic Aids:
^ Inspect the canister for cracks or fuel saturation

^ Inspect fuel vapor lines from the fuel tank or intake for leaks, being disconnected or sharp bends blocking the flow of vapors.