1999 Saturn SL2 Automatic, MP6FACTORY OEM SERVICE PROCEDURE

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. Turn ignition on, with engine off. Using scan tool, read MAF sensor voltage. If voltage is greater than 4.8 volts, go to step  7. If voltage is 4.8 volts or less, go to next step.
  3. Start engine and allow it to reach normal operating temperature. With engine idling, monitor MAF sensor voltage on scan tool. If MAF sensor voltage is less than 0.2 volt, go to step  12. If MAF sensor voltage is 0.2 volt or greater, go to next step.
  4. Check for air leaks between MAF sensor and throttle body. Repair as necessary. After repairs, go to step  27. If no problem is found, go to next step.
  5. Move/wiggle harness and related connectors while monitoring MAF sensor voltage on scan tool. If movement changes MAF sensor voltage, go to step  16. If movement does not change MAF sensor voltage, go to next step.
  6. Turn ignition on, with engine off. Review FREEZE FRAME data for DTC P0100 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 P0100 is set, go to step  23. If DTC P0100 is not set, go to step  28.
  7. Turn ignition off. Disconnect MAF sensor connector. Turn ignition on. If scan tool displays zero volts, go to next step. If scan tool does not display zero volts, go to step  11.
  8. 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  17.
  9. Using a test light connected to ground, probe signal return circuit at MAF sensor harness connector. If test light illuminates, go to step  24. If test light does not illuminate, go to next step.
  10. 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  25. If continuity is not present, go to step  18.
  11. Turn ignition off. Disconnect ECM harness connectors. Turn ignition on, with engine off. Using DVOM, check for voltage between ground and signal circuit at MAF sensor harness connector. If voltage is present, go to step  19. If voltage is not present, go to step  26.
  12. Disconnect MAF sensor. Using test light connected to battery positive, probe 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  14.
  13. Using test light connected to ground, probe battery feed circuit at MAF sensor harness connector. If test light illuminates, go to step  23. If test light does not illuminate, go to step  20.
  14. 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  21.
  15. Using DVOM, check for continuity between MAF sensor signal circuit and ground. If continuity is present, go to step  22. If continuity is not present, go to step  25.
  16. Repair harness or connections as necessary. After repairs, go to step  27.
  17. Repair open or high resistance in ground circuit. After repairs, go to step  27.
  18. Repair open or high resistance in signal return circuit. After repairs, go to step  27.
  19. Repair short to voltage in signal circuit. After repairs, go to step  27.
  20. Repair open or high resistance in switched battery feed circuit. After repairs, go to step  27.
  21. Repair open or high resistance in signal circuit. After repairs, go to step  27.
  22. Repair short to ground in signal circuit. After repairs, go to step  27.
  23. Check for poor connections and terminal tension at MAF sensor harness connector. Repair as necessary. After repairs, go to step  27. If no problem is found, go to next step.
  24. Replace MAF sensor. After repairs, go to step  27.
  25. Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step  27. If no problem is found, go to next step.
  26. Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After repairs, go to next step.
  27. 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 P0100 is set, go to step  2. If DTC P0100 is not set, go to next step.
  28. 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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When to See a Mechanic

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.

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