Evaporative Emissions System: Testing and Inspection

Chart C-3:

Canister Purge Valve Wiring Diagram:

CANISTER PURGE VALVE CHECK

CIRCUIT DESCRIPTION:

The canister purge is controlled by a solenoid that allows vacuum to purge the fuel vapor canister when energized. The ECM controls the ground to power the solenoid. If the diagnostic test terminal is grounded with the engine not running, or the following exists with the engine running, the purge solenoid is energized:

1. The engine run time is more than 30 seconds.
2. The coolant temperature is above 70~C (158~F).
3. The vehicle is in Closed Loop operation.




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

1. This checks to see if the solenoid is opened or closed. It should be closed (de-energized).
2. This completes a functional check by grounding the test terminal. This should normally energize the solenoid and allow the vacuum to drop.
3. This checks for an open or a shorted solenoid circuit.

NOTE: Once the test sequence is completed, clear codes and verify NO "SERVICE ENGINE SOON" light exists.




INCORRECT OPERATION MAY CAUSE:

1. Poor idle, stalling and poor driveability. Check for:

a. Inoperative or defective purge valve or solenoid
b. Damaged canister
c. Hoses split, cracked or not connected to the proper tubes
d. Pinched or plugged hose(s).