Canister Purge Solenoid: Testing and Inspection

Chart C-3 - Canister Purge Valve Check:

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

CHART C-3 TESTING CANISTER PURGE SOLENOID

Circuit Description:
Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when energized. The ECM supplies a ground to energize the solenoid (purge "OFF"). The purge solenoid control by the ECM is pulse width modulated (turned "ON" and "OFF" several times a second). The duty cycle (pulse width) is determined by the amount of air flow, and the engine vacuum as determined by the MAP sensor input. The duty cycle is calculated by the ECM and the output commanded when the following conditions have been met:

Engine run time run time less than specified.

Coolant temperature below a given value.

Vehicle speed below a given value.

TPS below a given value.




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

1. The solenoid should be pulsing as grounding the diagnostic terminal turns "ON" the solenoid.

2. Test light should light if circuit 439 is not open as the test light provides a ground for current flow.

3. Test light is being substituted for solenoid to check if ECM and CKT 428 are OK.

4. Solenoid is turned "OFF" and is normally open so vacuum reading should be zero inches.

5. Applying 12 volts prevents solenoid from pulsing, allowing some vacuum build-up before bleeding "OFF" internally 3" to 5".