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Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. 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, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Is the cooling system low on coolant? If yes, diagnose and repair cause of coolant loss. If no, go to next step.
  3. Turn ignition off. Disconnect ECT sensor. Connect a 3-amp fused jumper wire between the signal circuit and low reference circuit of ECT sensor harness connector. Turn ignition on, with engine off. Observe ECT sensor temperature with a scan tool. Does scan tool indicate that ECT sensor temperature is greater than 280°F (138°C)? If yes, go to next step. If no, go to step  5.
  4. Turn ignition off. Disconnect IAT sensor. Connect a 3-amp fused jumper wire between the signal circuit and low reference circuit of IAT sensor harness connector. Turn ignition on, with engine off. Observe IAT sensor temperature with a scan tool. Does scan tool indicate that IAT sensor temperature is greater than 280°F (138°C)? If yes, go to step  8. If no, go to DIAGNOSTIC AIDS .
  5. Turn ignition off. Disconnect ECT sensor. Connect a 3-amp fused jumper wire between the ECT sensor signal circuit and a known-good ground. Turn ignition on, with engine off. Observe ECT sensor temperature with a scan tool. Does the scan tool indicate that the ECT sensor temperature is greater than 280°F (138°C)? If yes, go to next step. If yes, go to step  7.
  6. Test ECT sensor low reference circuit for a high resistance or an open. Repair circuit as necessary. After repairs, go to step  11.
  7. Test ECT sensor signal circuit for a high resistance or an open. Repair circuit as necessary. After repairs, go to step  11.
  8. Remove ECT sensor. Suspend ECT sensor and a thermometer in a pan of water. Place pan on a burner or hot plate. Test the resistance of the ECT sensor through the specified range of 50-104°F (10-90°C). Does the resistance and temperature closely match the Engine Coolant Temperature Sensor Resistance table? See ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE  table. If yes, go to next step. If no, go to step  10.
  9. Reinstall ECT sensor. When complete, go to DIAGNOSTIC AIDS .
  10. Replace ECT sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
  11. Use the scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  12. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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