Diagnostic Procedures
- Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
- Observe the fuel Tank Pressure Sensor parameter on the scan tool. Remove the fuel filler cap. Is the fuel tank pressure within 0.0-0.5 in. H2O (0.0-0.9 mm Hg ) with the fuel filler cap removed? If yes, go to next step. If no, go to DTC P0451: FUEL TANK PRESSURE SENSOR PERFORMANCE .
- Turn ignition off. Disconnect the electrical connector from the EVAP canister purge valve. Measure the resistance of the EVAP canister purge valve using a DVOM. Is the resistance within 28-36 ohms at 68°F (20°C)? If yes, go to next step. If no, go to step 11.
- Turn ignition on, with engine off. Probe the ignition positive voltage circuit at the purge valve electrical connector with a test light connected to ground. Does the test light illuminate? If yes, go to next step. If no, go to step 7.
- Connect the electrical connector to the EVAP canister purge valve. Clear the DTCs using a scan tool. Backprobe the purge valve control circuit with a test light connected to battery voltage. Command the purge valve ON using a scan tool. Adjust the duty cycle from zero to 100 percent while observing the test light. Does the test light flash and then illuminate steadily at the 100 percent duty cycle? If yes, go to step 8. If no, go to next step.
- Check for an open or a short in the purge valve control circuit. Repair as necessary. Was a repair necessary? If yes, go to step 13. If no, go to step 12.
- Check for an open in the ignition positive voltage circuit. Repair as necessary. After repairs, go to step 13.
- Check the EVAP purge line between the intake manifold and EVAP canister for blockage. Was a repair necessary? If yes, go to step 13. If no, go to next step.
- Check the EVAP canister for restrictions or blockages. Did the canister pass all tests? If yes, go to step 12. If no, go to next step.
- Replace EVAP canister. After repairs, go to step 13.
- Replace EVAP canister purge valve. After repairs, go to step 13.
- Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE under PROGRAMMING. After replacing PCM, go to next step.
- Turn ignition off. Remove DOME fuse (located in passenger compartment fuse block). Reinstall DOME fuse. Reset radio clock time. Start engine. Operate the vehicle within the Conditions for Running the DTC or until the DTC P0496 diagnostic test has run. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step 2.
- With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.