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Home >> Oldsmobile >> 2000 >> Intrigue GL >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0171: Fuel Trim System Lean >> 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. After performing OBD system check, go to next step.
  2. Check if other DTCs are also set. If other DTCs are set, diagnose affected DTCs first. If no other DTCs are set, go to next step.
  3. Start and operate vehicle in closed loop mode. Using scan tool, monitor long term and short term fuel trim values. If value is greater than +15%, go to step  5. If value is not greater than +15%, go to next step.
  4. Using scan tool, review FAILURE RECORDS data. Clear DTCs. Operate vehicle within conditions in FAILURE RECORDS. If scan tool indicates that this test ran and passed, see DIAGNOSTIC AIDS . If scan tool does not indicate that this test ran and passed, go to next step.
  5. Check vacuum hoses for splits, kinks or improper routing. Repair as necessary. After repairs, go to step  22. If vacuum hoses are okay, go to next step.
  6. Check PCV system for proper installation and operation. Repair as necessary. After repairs, go to step  22. If PCV system is okay, go to next step.
  7. Check throttle body, air duct and MAF sensor for damage or restriction. Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  8. Start engine. Observe idle quality. If idle is high or unsteady, go to next step. If idle quality is okay, go to step  11.
  9. Using scan tool, observe IAC position with engine at idle. If IAC position is greater than 5 counts, go to step  11. If IAC position is not greater than 5 counts, go to next step.
  10. Check throttle body, intake manifold, EGR valve and EGR feed pipes for vacuum leaks. Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  11. Check idle air control system operation. Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  12. Check fuel for excessive water, alcohol or other contaminants. Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  13. Check PCM injector grounds, power grounds and sensor grounds. Ensure they are tight and clean and in their proper locations. Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  14. Disconnect MAF sensor harness connector. Operate vehicle in closed loop mode. Using scan tool, monitor short term fuel trim. If short term fuel trim decreases to about zero percent, go to step  21. If short term fuel trim does not decrease to about zero percent, go to next step.
  15. Perform EVAP system test. See DTC P0440: EVAPORATIVE EMISSION (EVAP) SYSTEM . Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  16. Perform fuel system pressure test. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  17. Check intake manifold, injector O-rings, EGR adapter, EGR valve and EGR feed pipes for vacuum leaks. Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  18. Check exhaust manifold for leaks, loose or missing hardware. Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  19. Check fuel injector operation. Perform injector balance test. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. After repairs, go to step  22. If no problem was found, go to next step.
  20. Check HO2S for proper installation. Check HO2S wiring harness for damage. Repair or replace as necessary. After repairs, go to step  22. If no problem was found, see DIAGNOSTIC AIDS .
  21. Replace MAF sensor. After replacing sensor, go to next step.
  22. Using scan tool, review and record FAILURE RECORDS data. Clear DTCs. Turn ignition off for 15 seconds. Operate vehicle within conditions required to set this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step  2.
  23. Using scan tool, review CAPTURED INFO. If other DTCs are present, go to applicable DTC. If no other DTCs are present, system is okay.
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