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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 89 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 4.0L)DIAGNOSTIC TESTSDTC P0440: EVAP SYSTEMDIAGNOSTIC PROCEDURES
1999 GMC Forward Control 5.7 R, Automatic

Diagnostic Procedures

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: EVAP Pressure/Purge Diagnostic Station (J- 41413) is required to pressurize EVAP system in the following test.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Does the scan tool indicate DTC P0443 or DTC P0449 are also set? If yes, see DTC P0443: EVAP PURGE SOLENOID CONTROL CIRCUIT  or DTC P0449: EVAP CANISTER VENT SOLENOID CONTROL CIRCUIT  . If no, go to next step.
  3. Inspect EVAP system for the following conditions.
    • Loose, missing or damaged service port Schrader valve.
    • Loose, incorrect, missing or damaged fuel filler cap.
    • A damaged EVAP canister purge valve.

    Raise and support vehicle. Inspect the EVAP system for the following:

    • Disconnected, improperly routed, kinked or damaged EVAP pipes and hoses.
    • Damaged EVAP canister vent valve or EVAP canister.

    Did you find and correct the condition? If yes, go to  18. If no, go to next step.

  4. With a scan tool, capture and record the Fail Record data and clear DTCs. Perform the Service Bay Test using scan tool. Does scan tool indicate that the Service Bay Test passed? If yes, see DIAGNOSTIC AIDS . If no, go to next step.
    5. NOTE: Always zero the EVAP pressure and vacuum (in H2O) gauges on the EVAP pressure diagnostic station before proceeding with diagnosis.
  5. Remove fuel filler cap. Install Fuel Tank Cap Adapter (J-41415). Connect EVAP Pressure/Purge Station (J-41413). Install vehicle fuel filler cap to fuel fill cap adapter. Zero pressure and vacuum gauges on EVAP pressure/purge station. Turn ignition on. Using scan tool, seal EVAP system. Using EVAP pressure/purge diagnostic station, pressurize system to 5 in. H2O. Rotate EVAP pressure/purge diagnostic station rotary switch to OFF/HOLD position. Monitor pressure gauge for one minute. Did you obtain and hold 5 in. H2O? If yes, go to next step. If no, go to step  8.
  6. Compare the J-41413 value to scan tool FTP sensor value. Does the J-41413 value measure near the scan tool value? If yes, go to next step. If no, go to step  12.
  7. Monitor the pressure gauge on the EVAP Pressure/Purge Diagnostic Station (J-41413). Disconnect EVAP purge pipe from EVAP purge valve. Does EVAP system pressure decrease? If yes, go to step  9. If no, go to step  10.
    8. NOTE: It may be necessary to partially lower fuel tank to inspect components located in the upper portion of tank.
  8. Continuously pressurize the EVAP system with the J-41413. Using Ultrasonic Leak Detector (J-41416), inspect for leaks in the following locations:
    • The EVAP system purge pipe.
    • The EVAP vapor pipe.
    • The EVAP vent hose/pipe.
    • The fuel fill pipe/hose and fuel fill cap.
    • The EVAP canister.
    • The EVAP canister vent valve.
    • The EVAP canister purge valve.
    • The fuel sender assembly and/or seal.
    • The FTP sensor seal.
    • The fill limiter vent valve, pressure relief valve, rollover valves, and/or fuel tank.

    Did you locate and repair a leak? If yes, go to step  18. If no, see DIAGNOSTIC AIDS .

  9. Connect a vacuum gauge to EVAP purge valve purge pipe port. Start engine and allow it to idle. Using scan tool, command EVAP canister purge valve to 50 percent. If vacuum gauge indicates an increase in vacuum, see DIAGNOSTIC AIDS . If vacuum gauge does not indicate an increase in vacuum, go to step  15.
  10. Monitor pressure gauge on EVAP pressure/purge diagnostic station. Disconnect purge pipe from EVAP canister. Does EVAP system pressure decreases? If yes, go to step  16. If no, go to next step.
  11. Monitor pressure gauge on EVAP pressure/purge diagnostic station. Disconnect vapor pipe from EVAP canister. Does the EVAP system pressure decrease? If yes, go to  17. If no, go to step  14.
  12. Using scan tool, monitor FTP sensor voltage. Is voltage more than 4.3 volts? If yes, go to DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE . If no, go to next step.
  13. Replace FTP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  18.
  14. Repair pinched or obstructed EVAP vapor pipe. After repairs, go to step  18.
  15. Replace EVAP canister purge valve. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  18.
  16. Repair restriction in EVAP purge pipe. After repairs, go to step  18.
  17. Replace EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
  18. Using scan tool, capture and record the Fail Record data and clear DTCs. Perform the Service Bay Test using scan tool. Does scan tool indicate that Service Bay Test passed? If yes, go to next step. If no, go to step  5.
  19. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.