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Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Check for DTC P0115 with a scan tool. Is DTC P0115 set? If yes, go to DTC P0115: ECT SENSOR CIRCUIT . If no, go to next step.
  3. Measure actual coolant temperature. Turn ignition switch to RUN position, engine OFF. Observe ECT sensor parameter on scan tool. Is ECT sensor value displayed near actual coolant temperature? If yes, go to step  11. If no, go to next step.
  4. Turn ignition OFF. Disconnect ECT sensor harness connector. Observe ECT sensor parameter on scan tool. Does engine coolant temperature equal -40°F (-40°C)? If yes, go to next step. If no, go to step  8.
  5. Disconnect ECT sensor 2-pin harness connector. Jump ECT sensor input circuit and ground circuit together at ECT sensor harness connector. Observe ECT sensor parameter on scan tool. Does engine coolant temperature equal 284°F (140°C)? If yes, go to step  13. If no, go to next step.
  6. Jump ECT sensor input circuit to chassis ground. Observe ECT sensor parameter on scan tool. Does engine coolant temperature equal 284°F (140°C)? If yes, go to next step. If no, go to step  8.
  7. Repair open or high resistance in ECT sensor ground circuit. Is the action complete? If yes, go to step  14. If no, go to step  9.
  8. Turn ignition OFF. Disconnect PCM White 34-pin harness connector C1. Check ECT sensor input circuit for a short or a high electrical resistance. Repair as necessary. Was a repair necessary? If yes, go to step  14. If no, go to next step.
  9. Check for a faulty connection at PCM and ECT harness connectors. Repair as necessary. Was a repair necessary? If yes, go to step  14. If no, go to next step.
  10. Replace PCM. After repair, go to step  14.
  11. Check engine cooling system for any of the following conditions:
    • A faulty thermostat.
    • A low engine coolant level.
    • The correct coolant solution.
    • Any faulty cooling system operation.
    Repair as necessary. See appropriate SPECIFICATIONS & DRIVE BELT ROUTING article under COOLING SYSTEM (MECHANICAL). Was a repair necessary? If yes, go to step  14. If no, go to next step.
  12. Use scan tool to clear DTCs. Place vehicle into CHECK MODE, using scan tool. See SERVICE BAY TESTS  under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as specified. Does DTC P0116 set? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  13. Replace ECT sensor. After repair, go to next step.
  14. Use scan tool to clear DTCs and road test vehicle within freeze frame conditions that set the DTC. Review scan tool data and check for DTCs. Repair is complete if no DTCs are stored. Are any DTCs displayed on scan tool? If yes, go to next step. If no, go to step  2.
  15. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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