Evaporative Emissions System: Testing and Inspection

Chart C-3:

EVAP Wiring Diagram:

CIRCUIT DESCRIPTION:
The canister purge is controlled by a solenoid that allows manifold vacuum to purge the fuel vapor canister when energized. The ECM supplies a ground to energize the solenoid (purge "ON"). The purge solenoid is energized (purge "ON") if the diagnostic "request" terminal is grounded with the engine stopped or the following is met with the engine running:

^ The engine run time after start is more than 45 seconds cold and/or 20 seconds when coolant temperature is greater than 85°C (185°F).
^ The engine coolant temperature is above 70°C (158°F).

TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. This checks to see if the solenoid is commanded opened or closed by the ECM. 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 the vacuum to drop (purge "ON").