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Home >> Oldsmobile >> 1998 >> Regency >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0125 - ECT Sensor Excessive Time To Reach Closed Loop >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Allow engine to cool completely. Turn engine on and allow it to idle. Using scan tool, monitor ENG COOL TEMP. If temperature increases to 70°F (21°C) within 2 minutes, see DIAGNOSTIC AIDS. If specified temperature is not reached within 2 minutes, go to next step.
  3. If any ECT related DTCs are set, diagnose affected DTC before proceeding. If no ECT related DTCs are set, go to next step.
  4. Allow engine to cool. Turn ignition on and observe cooling fans. If cooling fans are off, go to next step. If cooling fans are on, diagnose and repair cooling fan problem.
  5. Check coolant level. If coolant level is low, go to step 9). If coolant level is okay, go to next step.
  6. Check thermostat operation. If thermostat is operating correctly, go to next step. If thermostat is not operating correctly, go to step 9).
  7. Compare actual coolant temperature with scan tool ECT value. If temperatures are within 5°F (3°C) of each other, go to step 9). If temperatures are not within 5°F (3°C) of each other, go to next step.
  8. Check for high resistance in wiring related to ECT sensor and for poor connections at ECT sensor and PCM. Repair as necessary. After repairs, go to step 11). If no problem is found, go to step 10).
  9. Repair cooling system as necessary. After repairs, go to step 11).
  10. Replace ECT sensor. After replacing sensor, go to next step.
  11. Allow engine to cool completely. Using scan tool, clear DTCs. Turn engine on and allow it to idle. Using scan tool, monitor ENG COOL TEMP. If temperature increases to 70°F (21°C) within 2 minutes, repair is complete. If specified temperature is not reached within 2 minutes, return to step 2).
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