2003 Saturn L300FACTORY OEM SERVICE PROCEDURE

Malfunction Indicator Light Always On: Procedure

  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn ignition OFF. Disconnect Engine Control Module (ECM). Turn ignition ON, with engine OFF. Observe the Malfunction Indicator Light (MIL). If MIL illuminated, go to next step. If MIL is not illuminated, go to step  5.
  3. Test the MIL control circuit for a short to ground. Did you find and correct a short to ground? If yes, go to step  6. If no, go to next step.
  4. Replace the Instrument Panel Cluster (IPC). See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Did you complete IPC replacement? If yes, go to step  6.
  5. Replace the ECM. See ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - SATURN "L" SERIES article. Did you complete ECM replacement? If yes, go to next step.
  6. Turn the ignition OFF for 30 seconds. Start the engine. Does the vehicle operate correctly without any unwanted MIL illumination, and without any stored DTCs? If yes, system is okay. If any DTCs are present, see DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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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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