Canister Purge Solenoid: Description and Operation

Canister Purge Solenoid Normally Closed:

PURPOSE:
The Canister Purge Solenoid is controlled by the ECM/PCM and allows manifold and/or ported vacuum to purge the fuel evaporative cannister when energized.

OPERATION:
The ECM/PCM operates a Pulse Width Modulated (PWM) solenoid to control vacuum to purge the canister. Under cold engine or idle conditions, the solenoid is turned "OFF" or "ON" by the ECM/PCM, depending on if it is a normally open or normally closed solenoid. This blocks or allows vacuum to the canister. The ECM/PCM may turn "ON" or "OFF" the solenoid valve and allow purge when the following conditions are met.

^ Engine coolant temperature above a certain temperature.
^ After the engine has been running a specified amount of time.

In some cases the ECM/PCM 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.
^ Ignition "ON," engine stopped, diagnostic terminal grounded.

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