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Home >> Oldsmobile >> 1998 >> Regency >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0442 - EVAP System (Small Leak Detected) >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. If other DTCs are set, diagnose affected DTCs before proceeding. If DTCs are not 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. H2O go to next step. If scan tool does not display zero in. H2O, repair faulty fuel tank sensor circuit.
  4. Zero pressure and vacuum gauges on EVAP Pressure/Purge Diagnostic Station (J 41413). Reinstall fuel cap. Read and record FAIL RECORDS data for DTC P0442. Clear DTCs. Connect EVAP pressure/purge diagnostic station to EVAP service port. Using scan tool, command EVAP vent solenoid ON (closed). Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 5 in. H2O. If specified pressure is achieved, go to next step. If specified pressure is not achieved, repair faulty fuel tank sensor circuit.
  5. Turn ignition on, engine off. Using scan tool, command EVAP vent solenoid ON (closed). Using EVAP pressure/purge diagnostic station pressurize EVAP system to 15 in. H2O. Monitor EVAP pressure/purge diagnostic station pressure gauge. Turn EVAP pressure/purge diagnostic station rotary switch to HOLD position. If pressure decreases to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not decrease as specified, 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-held 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 to EVAP canister. If vacuum is maintained as specified, go to step 9). If vacuum cannot be maintained as specified, go to next step.
  7. Check if vent hose is disconnected or damaged. Check EVAP canister for damage. Repair as necessary. After repairs, go to step 11). If no problem is found, go to next step.
  8. Replace EVAP vent solenoid. After replacing solenoid, go to step 11).
  9. Check for missing or faulty fuel filler cap. Check for disconnected, leaking or damaged fuel tank vapor line or EVAP purge line. Repair as necessary. After repairs, 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 diagnostic station connected to EVAP service port, attempt to pressurize EVAP system by leaving diagnostic station control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J 41416), locate and repair EVAP system leak. It may be necessary to lower fuel tank to check connections at top of tank. After performing OBD system check, go to next step.
  11. Turn ignition on, engine off. Using scan tool, command EVAP vent solenoid on (closed). Using EVAP pressure/purge diagnostic station pressurize EVAP system to 15 in. H2O. Monitor diagnostic station pressure gauge. Turn EVAP pressure/purge diagnostic station rotary switch to HOLD position. If pressure decreases to less than 10 in. H2O within 2 minutes, repeat step 3). If pressure does not decrease to less than 10 in. H2O within 2 minutes, repair is complete.
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