Diagnostic Aids

An intermittent may be caused by a cracked or punctured EVAP canister, damaged or disconnected vacuum, vent or purge line. Check for poor connection, rubbed-through wire insulation or a broken wire inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. See BASIC DIAGNOSTIC PROCEDURES article. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
2. If any other DTCs are set, diagnose affected DTC(s) before proceeding. If no other DTC are set, go to next step.
3. Turn ignition off. Remove fuel cap. Turn ignition on. Using scan tool, read FUEL TANK PRESSURE. If scan tool displays zero in. H₂ O go to next step. If scan tool does not display zero in. H₂ O, repair faulty fuel tank pressure sensor circuit.
4. Zero pressure and vacuum gauges on EVAP Pressure/Purge Cart (J41413). Reinstall fuel cap. Read and record FAIL RECORDS data for DTC P0442. Clear DTCs. Connect EVAP pressure/purge cart to EVAP service port. Using scan tool, command EVAP vent solenoid ON (closed). Using EVAP pressure/purge cart, pressurize EVAP system to 5 in. H₂ O. If specified pressure is achieved, go to next step. If specified pressure is not achieved, repair faulty fuel tank pressure sensor circuit.
5. Start engine and allow to idle. Using scan tool, command EVAP vent solenoid ON (closed). Using EVAP pressure/purge cart pressurize EVAP system to 15 in. H₂ O. Monitor EVAP pressure/purge cart pressure gauge. Turn EVAP pressure/purge cart rotary switch to HOLD position. If pressure decreases to less than 10 in. H₂ O within 2 minutes, go to next step. If pressure does not decrease as specified, check for an intermittent problem. See DIAGNOSTIC AIDS .
6. Disconnect fuel tank vapor and EVAP purge lines from EVAP canister. Plug fuel tank vapor line fitting at EVAP canister. Connect a hand vacuum pump to EVAP purge line fitting at EVAP canister. Ensure EVAP vent solenoid is still commanded ON (closed). Attempt to apply 5 in. Hg vacuum to EVAP canister. If vacuum is maintained as specified, go to step  9. If vacuum can not be maintained as specified, go to next step.
7. Check if vent hose is disconnected or damaged. Check EVAP canister for damage. If a problem is found, repair as necessary and go to step  11. If no problem is found, go to next step.
8. Replace EVAP vent solenoid and go to step  11.
9. Check for missing or faulty fuel cap. Check for disconnected or leaking fuel tank vapor line. Check for disconnected or damaged EVAP purge line. If a problem is found, repair as necessary and go to step 11. If no problem is found, go to next step.
10. Using scan tool, command EVAP vent solenoid on (closed). With EVAP pressure/purge cart connected to EVAP service port, attempt to pressurize EVAP system by leaving EVAP pressure/purge cart control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J41416), locate and repair EVAP system leak. It may be necessary to lower fuel tank to check connections at top of tank. Go to next step.
11. Turn ignition on, engine off. Using scan tool, command EVAP vent solenoid on (closed). Using EVAP pressure/purge cart pressurize EVAP system to 15 in. H₂ O. Monitor EVAP pressure/purge cart pressure gauge. Turn EVAP pressure/purge cart rotary switch to HOLD position. If pressure decreases to less than 10 in. H₂ O within 2 minutes, return to step  3. If pressure does not decrease as specified, repair is complete.