Evaporative Emissions System: Testing and Inspection

Chart C-3 Evaporative Emission Canister Purge Solenoid Check:

EVAP Canister Purge Control Wiring Diagram:

Circuit Description:

EVAP canister purge is controlled by a solenoid valve that allows manifold vacuum to purge the EVAP canister when energized. The ECM supplies a ground to energize the solenoid valve.

If the diagnostic "test" terminal is grounded with the engine stopped and ignition "ON," or the following conditions are met with the engine running, the EVAP canister purge solenoid valve will be energized (purge "ON").

^ Engine run time after start more than 1 minute.
^ Engine coolant temperature above 60°C (140°F).
^ Vehicle speed above 1.3 mph.
^ Throttle off idle, above 6%.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. Checks to see if the solenoid valve is opened or closed. The solenoid valve is normally closed and should open when the diagnostic "test" terminal is grounded.

2. Completes functional check by grounding the diagnostic "test" terminal. This should energize the solenoid valve and allow the vacuum to drop (purge "ON").

3. Checks for a complete circuit. Normally, there is ignition voltage on CKT 541 and the ECM provides a ground on CKT 428. A shorted solenoid valve could cause an open circuit in the ECM.

Diagnostic Aids:


Normal operation of the EVAP canister purge solenoid valve is described as follows:

With the ignition "ON," engine "OFF," diagnostic "test" terminal grounded, the EVAP canister purge solenoid valve should be energized.