Chart C3 - Canister Purge Check

Canister purge is controlled by a solenoid that allows manifold vacuum to purge canister when de-energized. The ECM supplies a ground to energize solenoid (purge off). If diagnostic test terminal is grounded with engine stopped with engine running, purge solenoid is de-energized (purge on).

1. Checks to see if the solenoid is opened or closed. The solenoid is, normally energized in this test, so it should be closed.
2. Checks for a complete circuit. Normally, there is battery voltage on circuit No. 39, and the ECM provides a ground on circuit No. 428. A shorted solenoid could cause an open circuit in the ECM.
3. Completes functional check, by grounding test terminal. Normally this should de-energize the solenoid and allow the vacuum to drop (purge "ON").
4. Solenoids, or relays, are turned on or off by the ECM internal electronic switches, called "Drivers". Each driver is part of a group of 4 called "Quad-Drivers". Failure of one can damage any other driver within the set. Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM "Driver". Using an ohmmeter, check solenoid coil resistance of all ECM controlled solenoids and relays before installing a replacement ECM.