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. If multiple DTCs are set, check fuse No. 49 (50-amp) located in ECM housing. If fuse is open, go to step  6. If fuse is okay, go to next step.
  3. Remove AIR pump relay. Turn ignition on, with engine off. Using a test light connected to ground, probe switched B+ circuit at relay harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step  7.
  4. Using a test connected to battery positive, probe AIR pump relay control circuit at relay harness connector. Using scan tool, command AIR pump on. If test light illuminates, go to next step. If test light does not illuminate, go to step  8.
  5. Replace AIR pump relay. After repairs, go to step  10.
  6. Check battery feed circuit for short to ground. Repair as necessary and replace fuse. After repairs, go to step  10.
  7. Check switched B+ circuit for an open or short to ground. Repair as necessary. After repairs, go to step  10.
  8. Check AIR pump relay control circuit for an open or short to ground. Repair as necessary. After repairs, go to step  10. If circuit is okay, go to next step.
  9. Replace ECM. Program replacement ECM using required equipment. After repairs, go to next step.
  10. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0418. Operate vehicle within conditions for setting 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.
  11. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test. If no undiagnosed DTCs are displayed, system is okay.
Factory Service Tools

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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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