DTC 31

- Chart Code 31 Canister Purge Solenoid Diagnosis.:

- Wiring Diagram for Code 31 Canister Purge Solenoid Diagnosis.:

CODE 31 CANISTER PURGE SOLENOID DIAGNOSIS (VIN Y)

CIRCUIT DESCRIPTION
Canister purge solenoid controls the raw fuel vapor into the intake manifold that the canister collects. The ECM pulses the purge solenoid at a controlled rate per the following:
a. Coolant temp. is greater than 70 degrees centigrate
b. Engine run time is greater than 36 seconds
The purge cycle is pulse width modulated and is incremented by 1% per second until the duty cycle reaches 100%.
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.