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Home >> GMC >> 1999 >> Yukon Base, 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - DTC P0100-P0134 >> DTC P0101 >> DTC P0101: MAF System Performance (3.0L "V" Body) >> Diagnostic Procedures

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 DTC P0120, P1120 or P1220 is also set, diagnose affected DTC first. If specified DTCs are not set, go to next step.
  3. If DTC P0100 is also set, diagnose DTC. If DTC P0100 is not set, go to next step.
  4. Start engine. While observing TP and MAF sensor signals on scan tool, quickly depress accelerator pedal to Wide Open Throttle (WOT) and release. If both parameters increase in value as WOT is performed, go to step  6. If both parameters do not increase in value as WOT is performed, go to next step.
  5. If MAF sensor signal did not increase in value during WOT, go to step  13. If TP signal did not increase in value during WOT, diagnose using DTC P1221.
  6. Turn ignition on, with engine off. Review FREEZE FRAME data for DTC P0101 and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate under conditions required to duplicate DTC, and as close to conditions recorded in FREEZE FRAME as possible. See CIRCUIT DESCRIPTION . Check for DTCs. If DTC P0101 is set, go to next step. If DTC P0101 is not set, see DIAGNOSTIC AIDS .
  7. Check for objects blocking MAF sensor inlet screen. Check for intake manifold and throttle body vacuum leaks or air leaks in intake duct system between MAF sensor and throttle body. Check PCV system operation. Check for loose or missing oil fill cap or unseated engine oil dipstick. Repair as necessary. After repairs, go to step  28. If no problems are found, go to next step.
  8. Turn ignition on, with engine off. Disconnect MAF sensor connector. If scan tool displays less than.5 volt, go to next step. If scan tool displays.5 volt or greater, go to step  12.
  9. Using DVOM, measure voltage between 5-volt reference circuit and ground circuit at MAF sensor harness connector. If voltage is greater than 4.5 volts, go to next step. If voltage is not as specified, go to step  18.
  10. Using a test light connected to battery positive, probe signal return circuit at MAF sensor harness connector. If test light illuminates, go to step  25. If test light does not illuminate, go to next step.
  11. Turn ignition off. Disconnect ECM harness connectors. Using DVOM, check for continuity in MAF sensor signal return circuit between ECM and MAF sensor harness connectors. If continuity is present, go to step  26. If continuity is not present, go to step  19.
  12. Turn ignition off. Disconnect ECM harness connectors. Turn ignition on, with engine off. Using DVOM, check for voltage on signal circuit at MAF sensor harness connector. If voltage is present, go to step  20. If voltage is not present, go to step  27.
  13. Disconnect MAF harness sensor. Using a test light connected to battery positive, probe MAF sensor signal circuit at MAF sensor harness connector. If scan tool displays 5 volts, go to next step. If scan tool does not display 5 volts, go to step  15.
  14. Using a test light connected to ground, probe MAF sensor battery feed circuit at MAF sensor harness connector. If test light illuminates, go to step  24. If test light does not illuminate, go to step  21.
  15. Turn ignition off. Disconnect ECM harness connectors. Using DVOM, check for continuity in MAF sensor signal circuit between ECM and MAF sensor harness connectors. If continuity is present, go to next step. If continuity is not present, go to step  22.
  16. Using DVOM, check for continuity between MAF sensor signal circuit and ground. If continuity is present, go to step  23. If continuity is not present, go to step  26.
  17. Repair harness connector or terminal connections as necessary. After repairs, go to step  28.
  18. Repair open or high resistance in ground circuit. After repairs, go to step  28.
  19. Repair open or high resistance in signal return circuit. After repairs, go to step  28.
  20. Repair short to voltage in signal circuit. After repairs, go to step  28.
  21. Repair open or high resistance in switched battery feed circuit. After repairs, go to step  28.
  22. Repair open or high resistance in signal circuit. After repairs, go to step  28.
  23. Repair short to ground in signal circuit. After repairs, go to step  28.
  24. Check for poor connections and terminal tension at MAF sensor harness connector. Repair as necessary. After repairs, go to step  28. If no problems are found, go to next step.
  25. Replace MAF sensor. After repairs, go to step  28.
  26. Check for poor connections and terminal tension at ECM harness connectors. Repair as necessary. After repairs, go to step  28. If no problems are found, go to next step.
  27. Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After repairs, go to next step.
  28. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate under conditions required to duplicate DTC. See CIRCUIT DESCRIPTION . Check for DTCs. If DTC P0101 is set, go to step  2. If DTC P0101 is not set, go to next step.
  29. If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC test. If no other DTCs are present, system is okay.
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