Computer Command Control (C-3) System

- Chart C-3 Canister Purge Solenoid Diagnosis.:

- Wiring Diagram for Chart C-3 Canister Purge Solenoid Diagnosis.:

CHART C-3 CANISTER PURGE CHECK (VIN Y)

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 "ON").
If the diagnostic test terminal is grounded with the engine stopped, the purge solenoid is energized (purge "ON").
Code 31 indicates the canister purge feedback input is not reading the correct voltage under the following conditions:
a. Purge solenoid "ON" when it should be "OFF".
b. Duty cycle at 100% when it should be 0%.
c. Above conditions less than or greater than a calibrated time in seconds.

CHART DESCRIPTION
1. Checks to see if the solenoid is opened or closed. The solenoid is normally de-energized in this step, so it should be closed.
2. Completes functional check by grounding test terminal. This should normally energize the solenoid and allow the vacuum to drop (purge "ON").
3. Checks for open or shorted solenoid circuit.
4. Checks to see if ECM control circuit or solenoid is at fault. Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause the CCP driver to open within the ECM as all QDRs are fault protected.
5. If the test light goes "OFF" with the ECM disconnected, the quad driver within the ECM is faulty and the ECM has to be replaced.