Diagnostic Procedures

1999 Saturn SL2 Automatic, MP6SECTION 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. Using scan tool, select FAILURE RECORDS and note ECT display. If ECT sensor reads less than -35°F (-37°C), diagnose using test for DTC P0117. If ECT sensor does not read less than -35°F (-37°C), go to next step.
  3. Start and warm engine to normal operating temperature. Using scan tool, select DATA LIST, ENGINE 1 and note ECT display while engine is warming up. If ECT reading is erratic or skipping (rapid changing), go to step  6. If ECT reading is normal, go to next step.
  4. After engine is fully warmed up (about 20 minutes), note ECT display. If ECT reading is less than 185°F (85°C), go to next step. If ECT reading is not less than 185°F (85°C), fault is not present at this time. See DIAGNOSTIC AIDS .
  5. Check ECT sensor ground and signal circuits for high resistance. Repair as necessary. If circuits are okay, repair cooling system.
  6. Check terminal contact at ECT sensor. Repair as necessary. If terminal contact is okay, go to next step.
  7. Replace ECT sensor.
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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.