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Home › Chevrolet › 2000 › Prizm Base, Standard › Repair and Diagnosis › Engine Performance › System › Engine Controls Self-Diagnostics - 1.8L › Diagnostic Tests › DTC P0125: ECT Excessive Time To Enter Closed Loop › Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Using scan tool, monitor HO2S-1 parameter. Snap throttle and monitor HO2S-1 voltage. If voltage varies within 200-900 millivolts, go to next step. If voltage does not vary within 200-900 millivolts, go to step  4 .
  3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC resets, go to next step. If DTC does not reset, see DIAGNOSTIC AIDS  .
  4. Disconnect HO2S-1 harness connector. Turn ignition on, with engine off. Set DVOM to DC volt scale. Connect DVOM positive lead to battery voltage. Connect negative lead to HO2S-1 connector (harness side) HO2S-1 input circuit. See WIRING DIAGRAMS article. Using scan tool, monitor HO2S-1 parameter. If scan tool voltage is greater than 1155 millivolts, go to next step. If scan tool voltage is 1155 millivolts or less, go to step  6 .
  5. Using test light connected to battery voltage, probe HO2S-1 connector (harness side) HO2S-1 ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step  8 . If test light does not illuminate, go to step  7 .
  6. Check for an open or short in HO2S-1 input circuit between HO2S-1 and PCM. Repair as necessary. After repairs, go to step  10 . If circuit is okay, go to step  9 .
  7. Repair open in HO2S-1 ground circuit between HO2S-1 and ground connection. Repair as necessary. After repairs, go to step  10 .
  8. Replace HO2S-1. After replacing sensor, go to step  10 .
  9. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTC(s).
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