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Home >> Buick >> 2002 >> Century Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.1L Engine >> Diagnostic Tests >> DTC P0125: ECT Excessive Time To Enter Closed Loop >> Diagnostic Procedures
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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 low on coolant? If yes, check 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 the low reference circuit of ECT sensor harness connector. Turn ignition on, with engine off. With a scan tool, observe the ECT sensor temperature. Does the scan tool indicate that the ECT sensor temperature is 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 wire between the signal circuit of the ECT sensor harness connector and a known-good ground. Turn ignition on, with engine off. Observe the ECT sensor temperature with a scan tool. Does the scan tool indicate that the ECT sensor temperature is more than 280°F (138°C)? If yes, go to next step. If no, go to step  6.
  5. Test ECT sensor low reference circuit for a high resistance or an open. Repair the circuit as necessary. After repairs, go to step  10.
  6. Test ECT sensor signal circuit for a high resistance or an open. Repair the circuit as necessary. After repairs, go to step  10.
  7. Remove ECT sensor. 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? Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article. If yes, go to next step. If no, go to step  9.
  8. Reinstall ECT sensor. When complete, diagnose thermostat operation.
  9. Replace ECT sensor. After replacing sensor, go to next step.
  10. Clear DTCs with scan tool. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  11. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay.
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