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Home › Pontiac › 2001 › Aztek Base, AWD › Repair and Diagnosis › Engine Performance › System › Engine Controls Self-Diagnostics › Diagnostic Tests › DTC P0440: Evaporative Emission System › Diagnostic Procedures

Diagnostic Procedures

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Using scan tool, recheck DTCs. If DTC P0443 or DTC P0449 is also set, diagnose affected DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If DTC P0443 or P0449 is not set, go to next step.
  3. Check 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 vehicle on hoist. Check EVAP system for disconnected, improperly routed, kinked or damaged EVAP pipes and hoses. Check for damaged or disconnected EVAP canister vent valve, or damaged or disconnected EVAP canister. Repair as necessary. After repairs, go to step  18. If no problem is found, go to next step.
  4. Using scan tool, clear DTCs, then perform the SERVICE BAY CHECK. If test passed, see DIAGNOSTIC AIDS . If test did not pass, go to next step.
    5. NOTE: Before testing, zero gauges on EVAP pressure diagnostic station.
  5. Connect Fill Tank Cap Adapter (J-41415-40) to fuel filler neck and fuel filler cap. Connect EVAP Pressure Diagnostic Station (J-41413) to adapter. Turn ignition on, with engine off. Using scan tool, seal the EVAP system. Using diagnostic station, pressurize the system to 5 in. H2O. Move rotary switch on diagnostic station to OFF/HOLD position. Monitor pressure gauge for one minute. If pressure is held at 5 in. H2O, go to next step. If pressure is not held at 5 in. H2O, go to step  8.
  6. Compare pressure reading between the diagnostic station and the scan tool's Fuel Tank Pressure (VTP) sensor value. If reading is close between the diagnostic station and scan tool, go to next step. If reading is not close between the diagnostic station and scan tool, go to step  13.
  7. Using diagnostic station, pressurize EVAP system to 5 in. H2O. Turn rotary switch on diagnostic station to OFF/HOLD position. Monitor pressure gauge on diagnostic station. Using scan tool, command EVAP canister purge valve to 50 percent. If EVAP system pressure decreases, go to step  9. If EVAP system pressure does not decrease, go to step  10.
  8. Continuously pressurize EVAP system. Using Ultrasonic Leak Detector (J-41416), check for leaks in EVAP system purge pipe, vapor pipe, vent hose/pipe, fuel fill pipe/hose, fuel fill cap, EVAP canister, EVAP canister vent valve, EVAP canister purge valve, fuel sender assembly and/or seal, VTP sensor seal, fill limiter vent valve, pressure relief valve, rollover valves, permanent EVAP pipes and/or fuel tank. Repair as necessary. After repairs, go to step  19. If no problem is found, see DIAGNOSTIC AIDS .
  9. Disconnect EVAP purge pipe from canister purge valve. Install vacuum hose from diagnostic station to the EVAP canister purge valve port. Operate engine at 1200-1500 RPM. Using scan tool, command EVAP canister purge valve to 50 percent. If EVAP diagnostic station vacuum gauge reading is greater than 12 in. Hg, see DIAGNOSTIC AIDS . If EVAP diagnostic station vacuum gauge reading is not greater than 12 in. Hg, go to step  15.
  10. Monitor pressure gauge on EVAP diagnostic station. Disconnect EVAP purge pipe from EVAP canister purge valve. If EVAP system pressure decreases, go to step  16. If EVAP system pressure does not decrease, go to next step.
  11. Monitor pressure gauge on EVAP diagnostic station. Disconnect purge pipe at EVAP canister. If EVAP system pressure decreases, clean EVAP system. If EVAP system pressure does not decrease, go to next step.
  12. Monitor pressure gauge on EVAP diagnostic station. Disconnect EVAP vapor line from EVAP canister. If EVAP system pressure decreases, go to step  17. If EVAP system pressure does not decrease, go to step  14.
  13. Replace VTP sensor. After replacing sensor, go to step  18.
  14. Repair pinched or obstructed EVAP vapor pipe. After repairs, go to step  18.
  15. Check vacuum source to EVAP purge valve for blockage, cuts or disconnects. Repair as necessary. After repairs, go to step  18. If no problem is found, go to next step.
  16. Replace EVAP canister purge valve. After replacing purge valve, go to step  18.
  17. Replace EVAP canister. After replacing canister, go to next step.
  18. Using scan tool, perform service bay check. If scan tool indicates that test passed, go to next step. If scan tool does not indicate that test passed, go to step  2.
  19. Using scan tool, observe the stored information and CAPTURE INFO. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay.
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