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Home › Saturn › 2003 › Ion 1 Standard › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P0125: Engine Coolant Temperature Excessive Time To Closed Loop Fuel Control › Diagnostic Procedures

Diagnostic Procedures

  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Is the cooling system coolant low? If yes, repair cause of coolant loss. If no, go to next step.
  3. Connect a 3-amp fused jumper wire between the signal circuit and the low reference circuit of the engine coolant temperature (ECT) sensor. Observe the ECT sensor parameter with a scan tool. Is the ECT sensor parameter more than 300°F (149°C)? If yes, go to step  7. If no, go to next step.
  4. Connect a 3-amp fused jumper wire between the signal circuit of the ECT sensor and a good ground. Observe the ECT sensor parameter with a scan tool. Is the ECT sensor parameter more than 300°F (149°C)? If yes, go to next step. If no, go to step  6.
  5. Test the ECT sensor low reference circuit for a high resistance or for an open. Did you find and correct the condition? If yes, go to step  10. If no, see DIAGNOSTIC AIDS .
  6. Test the ECT sensor signal circuit for a high resistance or for an open. Did you find and correct the condition? If yes, go to step  10. If no, see DIAGNOSTIC AIDS .
  7. Remove the ECT sensor. See ENGINE COOLANT TEMPERATURE SENSOR under SENSORS & SWITCHES in REMOVAL & INSTALLATION - ION article. Suspend the ECT sensor and a thermometer in a pan of water. Place the pan on a burner or hot plate. Test the resistance of the ECT sensor through the specified range of 50-194°F (10-90°C). Does the resistance and temperature closely match the Temperature vs Resistance table? See TEMPERATURE VS. RESISTANCE . If yes, go to next step. If no, go to step  9.
  8. Install the ECT sensor. After installing ECT sensor, diagnose engine cooling thermostat.
  9. Replace the ECT sensor. After replacing sensor, go to next step.
  10. Using scan tool, clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  11. Using the scan tool, observe the CAPTURE INFO. Does the scan tool display any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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