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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 88 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L)DIAGNOSTIC TESTSDTC P0440: EVAP SYSTEMDIAGNOSTIC PROCEDURES
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Procedures

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 GMC Sonoma and 2002 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Are DTCs P0446, P0452, P0453, or P1441 also set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Inspect the EVAP system for loose, missing, or damaged service port Schrader valve. Check for loose, incorrect, missing, or damaged fuel fill cap. Check for damaged EVAP canister purge valve. Raise the vehicle on a hoist. Inspect the EVAP system for disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses. Check for damaged EVAP canister vent valve or EVAP canister. Did you find and correct the condition? If yes, go to step  33. If no, go to next step.
  4. Use the scan tool in order to clear the DTCs. Command the EVAP canister purge valve to 50 percent and back to 0 percent with the scan tool. Do you hear or feel a clicking from the EVAP purge valve when it is commanded to 50 percent? If yes, go to next step. If no, go to step  6.
  5. Command the EVAP canister vent valve ON and OFF with the scan tool. Do you hear or feel a click as the EVAP vent valve is commanded ON and OFF? If yes, go to step  10. If no, go to step  8.
  6. Disconnect the EVAP purge valve harness connector. Turn ON the ignition, with engine OFF. Connect a test light between the ignition voltage circuit of the EVAP purge valve and a known-good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  24.
  7. Connect a test light between the ignition voltage circuit and the control circuit of the EVAP purge valve. Command the EVAP purge valve to 50 percent and then to 0 percent with a scan tool. Does the test light illuminate or pulsate when the EVAP purge valve is commanded to 50 percent and turn OFF when the EVAP purge valve is commanded to 0 percent? If yes, go to step  19. If no, go to step  17.
  8. Turn ignition on, with engine off. Disconnect the EVAP vent valve harness connector. Connect a test light between the EVAP vent valve ignition voltage circuit and a known-good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  25.
  9. Connect the test light between the ignition voltage circuit and the control circuit of the EVAP vent valve. Command the EVAP vent valve ON, with a scan tool. Does the test light illuminate when the EVAP vent valve is commanded ON? If yes, go to step  20. If no, go to step  18.
  10. Turn ignition off. Disconnect the EVAP purge pipe from the EVAP purge valve. Connect a vacuum gauge directly to the EVAP purge connection of the EVAP purge valve. Start engine. Increase the engine speed to 1500 RPM. Command the EVAP canister purge valve to 50 percent with a scan tool. Is the vacuum at or greater than 15 in. H2O? If yes, go to next step. If no, go to step  23.
    11. NOTE: Always zero the EVAP pressure and vacuum (in. H2O) gauges on the J-41413 EVAP Pressure/Purge Diagnostic Station before proceeding with diagnosis.
  11. Reconnect the EVAP purge pipe to the EVAP canister purge valve. Install the Fuel Tank Cap Adapter (J-41415-40). Connect the J-41413 and vehicle fuel fill cap to the J-41415-40. Turn ON ignition, with engine OFF. Use a scan tool in order to seal the EVAP system. Using the J-41413, attempt to pressurize the EVAP system to the specified value. Rotate the J-41413 rotary switch to the OFF/HOLD position. Were you able to obtain and hold the specified value for 1 minute? If yes, go to next step. If no, go to step  13.
  12. Compare the EVAP pressure/purge diagnostic station pressure gauge value to the scan tool FTP sensor value. Does the EVAP pressure/purge diagnostic station gauge value correspond to the FTP sensor value on scan tool ? If yes, go to step  14. If no, go to step  16.
  13. Using Diagnostic Station (J-41413), continuously attempt to pressurize EVAP system. It may be necessary to partially lower fuel tank to check components located in upper portion of tank. Using an Ultrasonic Leak Detector (J-41416), check for leaks in EVAP system purge pipe, vapor pipe, vent hose/pipe, fuel fill pipe/hose and fuel fill cap. Check EVAP canister vent valve, canister purge valve, fuel sender assembly and/or seal. Check the fill limiter vent valve, pressure relief valve, rollover valves and fuel tank. Did you find and repair the condition? If yes, go to step  33. If no, see DIAGNOSTIC AIDS .
  14. Monitor diagnostic station. Disconnect EVAP purge pipe from EVAP canister. Does pressure reading on gauge decreases to about zero in. H2O? If yes, go to step  26. If no, go to next step.
  15. Observe pressure gauge on diagnostic station. Disconnect EVAP vapor line from EVAP canister. Does pressure reading on gauge decreases to about zero in. H2O? If yes, go to step  30. If no, go to step  27.
  16. Is the FTP sensor value greater than 4.3 volts? If yes, go to DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE . If no, go to step  21.
  17. Test the control circuit of the EVAP purge valve for an open or short to voltage. Did you find and correct the condition? If yes, go to step  33. If no, go to step  22.
  18. Test the control circuit of the EVAP vent valve for an open or short to voltage. Did you find and correct the condition? If yes, go to step  33. If no, go to step  22.
  19. Test for poor connections at the harness connector of the EVAP purge valve. Did you find and correct the condition? If yes, go to step  33. If no, go to step  28.
  20. Test for poor connections at the harness connector of the EVAP vent valve. Did you find and correct the condition? If yes, go to step  33. If no, go to step  29.
  21. Test for poor connections at the harness connector of the FTP. Did you find and correct the condition? If yes, go to step  33. If no, go to step  31.
  22. Check for poor connections PCM harness connector. Did you find and correct the condition? If yes, go to step  33. If no, step  32.
  23. Inspect the vacuum source to the EVAP purge valve for blockage, cuts, or disconnects. Repair as necessary. Did you find and correct the condition? If yes, go to step  33. If no, go to step  28.
  24. Repair the ignition voltage circuit of the EVAP purge valve for an open or short to ground. Replace the fuse as necessary. After repairs, go to step  33.
  25. Repair the ignition voltage circuit of the EVAP vent valve for an open or short to ground. Replace the fuse as necessary. After repairs, go to step  33.
  26. Repair restriction in EVAP purge pipe. After repairs, go to step  33.
  27. Repair restriction in EVAP vapor pipe. After repairs, go to step  33.
  28. Replace EVAP purge valve. After replacing EVAP purge valve, go to step  33.
  29. Replace EVAP vent valve. After replacing EVAP vent valve, go to step  33.
  30. Replace EVAP canister. After replacing EVAP canister, go to step  33.
  31. Replace FTP sensor. After replacing FTP sensor, go to step  33.
  32. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  33. Turn ignition on, with engine off. Using scan tool, command EVAP vent valve on. Using EVAP pressure/purge diagnostic station, pressurize EVAP system. Place control knob on EVAP pressure/purge diagnostic station to OFF/HOLD position. Monitor EVAP system pressure on diagnostic station for 5 minutes. Does the EVAP system pressure remain constant? If yes, go to next step. If no, go to step  4.
  34. Using scan tool, observe stored information and capture information. Does the scan tool display any DTCs that you have not diagnosed? If yes, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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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.