Chart C-3 Canister Purge Check

Chart C-3:

Canister Purge Solenoid Circuit:

CIRCUIT DESCRIPTION:

Canister purge is controlled by a solenoid that allows manifold and/or ported vacuum to purge the canister when energized. The Electronic Control Module (ECM) supplies a ground to energize the solenoid (purge "ON"). The purge solenoid control by the ECM is turned "ON" or "OFF" under specific engine conditions. The purge solenoid is turned "ON" when all of the following conditions are met:

^ ALDL is ungrounded.
^ Engine run time after start more than 20 seconds.
^ Coolant temperature above 60°C.
^ Vehicle speed is above 15 mph.

Also, if the diagnostic test terminal is grounded with the engine stopped, the purge solenoid is energized (purge "ON").

TEST DESCRIPTION: Numbers below refer to the 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. Checks to determine if solenoid was open due to electrical circuit problem or defective solenoid.

3. Completes functional check by grounding test terminal. This should normally energize the solenoid opening the valve which should allow the vacuum to drop (purge "ON").

DIAGNOSTIC AIDS:

Make a visual check of vacuum hoses. Check throttle body for possible cracked, broken, or plugged vacuum block. Check engine for possible mechanical problem.