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Home >> GMC >> 1999 >> Forward Control 6.5 F, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - DTC P0352-P0452 >> DTC P0440 >> DTC P0440: EVAP System (5.7L "F" Body) >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. If any other EVAP system DTCs are stored as history DTC, diagnose applicable DTC. If other EVAP system related DTCs are not present, go to next step.
  3. Check EVAP system for loose, incorrect, defective or missing fuel tank filler cap. Check for improperly routed, kinked or damaged EVAP system purge lines or damaged EVAP system component. Repair or replace as necessary. After repairs, go to step  18. If repairs were not necessary, go to next step.
  4. Using scan tool, perform EVAP system SERVICE BAY TEST. If vehicle passes test, see DIAGNOSTIC AIDS . If vehicle fails test, go to next step.
  5. Turn ignition off. Remove EVAP purge solenoid valve from intake manifold. Install a vacuum gauge to vacuum source. Start and operate engine at idle. If vacuum reading is 12 in. Hg or greater, go to next step. If vacuum reading is not 12 in. Hg or greater, go to step  12.
  6. Turn ignition off. Install vacuum gauge to EVAP canister side of EVAP purge solenoid valve. Start and operate engine at idle. Using scan tool, command EVAP vent solenoid 100 percent. If vacuum gauge reads 12 in. Hg or greater, go to next step. If vacuum gauge does not read 12 in. Hg or greater, go to step  13.
  7. Turn ignition off. Disconnect fuel tank vapor and EVAP purge line from EVAP canister. Plug canister fitting for fuel vapor line. Connect a hand-held vacuum pump to EVAP purge line on canister. Turn ignition on. Using scan tool, command EVAP vent valve on (closed). Using vacuum pump, apply 5 in. Hg. If specified vacuum can be obtained and held, go to step  10. If vacuum cannot be obtained or held, go to next step.
  8. Disconnect vent line at EVAP vent valve. Plug vent line. Apply 5 in. Hg using vacuum pump. If vacuum can be obtained and held, go to step  14. If vacuum cannot be obtained or held, go to next step.
  9. Check EVAP vent line from canister to EVAP vent valve for leaks. Repair as necessary. After repairs, go to step  18. If leak is not present, go to step  15.
  10. Turn ignition off. Remove hand-held vacuum pump. Reconnect EVAP canister purge and vent valve lines. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to EVAP system service port. Ensure gauges are zeroed on diagnostic station. Using scan tool, command EVAP vent solenoid ON (closed). Continuously attempt to pressurize EVAP system by leaving EVAP pressure/purge 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 repairs, go to step  18. If leaks are not present, go to next step.
  11. Check EVAP system for restrictions. Repair as necessary. After repairs, go to step  18. If no restrictions are found, go to step  16.
  12. Locate and repair leak at vacuum source to EVAP purge solenoid valve. After repairs, go to step  18.
  13. Check EVAP purge solenoid valve and purge line for carbon contamination. Replace EVAP purge solenoid valve. After replacing solenoid valve, go to step  18.
  14. Replace EVAP vent valve. After replacing vent valve, go to step  18.
  15. Replace EVAP vapor canister. After replacing vapor canister, go to step  18.
  16. With EVAP system pressurized, compare EVAP pressure/purge diagnostic station pressure gauge reading to fuel tank pressure sensor reading on scan tool. Also, compare reading with system depressurized. If fuel tank pressure sensor indicate the actual amount of pressure in EVAP system, repeat step  13. If fuel tank pressure sensor pressure does not indicate the actual amount of pressure in EVAP system, go to next step.
  17. Replace fuel tank pressure sensor. After replacing sensor, go to next step.
  18. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter DTC P0440. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step  2.
  19. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.
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