Canister Purge Control Valve: Testing and Inspection

Chart C-3 - Canister Purge Valve Check:

Wiring Diagram for Chart C-3 - Canister Purge Valve Check:

CHART C-3 CANISTER PURGE VALVE CHECK

CIRCUIT DESCRIPTION:

The 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, controlled by the ECM, is pulse width modulated (turned "ON" and "OFF" several times a second). The duty cycle (pulse width) is determined by "Closed loop" feedback from the oxygen sensor. If the diagnostic test terminal is grounded with the engine stopped, the purge solenoid is energized (purge "ON"). The duty cycle is calculated by the ECM and the output command is sent when the following conditions have been met:
a. The engine run time after start is more than 65 seconds.
b. Coolant temperature is above 56~C.

TEST DESCRIPTION: The numbers below refer to the circled numbers on the diagnostic chart.
1. This 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. This checks to determine if the solenoid was open due to an electrical circuit problem or defective solenoid.
3. This completes the functional check by grounding the test terminal. This should normally energize the solenoid opening in the valve which should allow the vacuum to drop (purge "ON").

DIAGNOSTIC AIDS:
Make a visual check of vacuum hoses. Check the throttle body for possible cracked, broken, or plugged vacuum block. Check the engine for possible mechanical problems.