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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 123 (Engine Controls - Self-Diagnostics - 4.0L) >> Diagnostic Tests >> DTC P0125: Engine Coolant Temperature Excessive Time To Reach Closed Loop >> Diagnostic Procedures

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. Check coolant level. If coolant level is okay, go to next step. If coolant level is low, check cooling system for leaks. Repair as necessary and top off coolant level.
  3. Turn ignition off. Disconnect ECT sensor. Connect a 3-amp fused jumper between the ECT sensor signal circuit and low reference circuit. Turn ignition on, with engine off. Use scan tool in order to observe the ECT sensor temperature. Is ECT sensor temperature more than 280°F (138°C)? If yes, go to step  7. If no, go to next step.
  4. Turn ignition off. Disconnect ECT sensor. Connect a 3-amp fused jumper between the ECT sensor signal circuit and a ground. Turn ignition on, with engine off. Using scan tool, observe ECT sensor temperature. Is ECT sensor temperature more than 280°F (138°C)? If yes, go to next step. If no, go to step  6.
  5. Test ECT sensor reference low circuit for a high resistance and for an open. Repair as necessary. After repairs, go to step  10.
  6. Test ECT sensor signal circuit for a high resistance and for an open. Repair the circuit as necessary. After repairs, go to step  10.
  7. 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 50-194°F (10-90°C). Do the resistance and the temperature closely match the Temperature vs Resistance Table? See ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE  table. If yes, go to next step. If no, go to step  9.
  8. Reinstall ECT sensor. Diagnose cooling system thermostat. Replace thermostat as necessary.
  9. Replace ECT sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
  10. 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.
  11. 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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