Canister Purge Solenoid: Description and Operation

Wiring Diagram:

The ECM operates a normally closed Pulse Width Modulated (PWM) solenoid to control vacuum to purge the canister. Under cold engine or idle conditions, the solenoid is turned "OFF" by the ECM, which blocks vacuum and prevents purge of the canister. The ECM turns "ON" the solenoid valve and allows purge when the following conditions are met.

^ Engine is warm.
^ After the the engine has been running a specified amount of time.

In some cases the ECM may also look for these conditions in addition to those listed above in order to purge the canister.

^ Above a specified road speed.
^ Above a specified throttle opening.

The ECM also uses input from the 02 sensor to regulate purging of the canister. The ECM also has diagnostic capabilities to set a Code 26 in the event of a disconnected or shorted wire.