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HOMESERVICE MANUALSCHEVROLET2000CAVALIER BASE, 2D COUPE, AUTOMATIC, 4T40E/MN4REPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L & 2.4LDIAGNOSTIC TESTSDTC P0125: ECT EXCESSIVE TIME TO ENTER CLOSED LOOP FUEL CONTROLDIAGNOSTIC PROCEDURES
2000 Chevrolet Cavalier Base, 2D Coupe, Automatic, 4T40E/MN4

Diagnostic Procedures

2000 Chevrolet Cavalier Base, 2D Coupe, Automatic, 4T40E/MN4SECTION 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. Turn ignition on, with engine off. Using scan tool, check if any DTCs are set. If any DTCs are set, diagnose affected DTC(s). If no other DTCs are set, go to next step.
  3. Using scan tool, check engine coolant temperature. If coolant temperature is 165°F (73°C) or greater, go to next step. If coolant temperature is not 165°F (73°C) or greater, go to step  5 .
  4. Check thermostat for proper operation. If thermostat is okay or after replacing thermostat, go to next step.
  5. Cool engine to ambient temperature. Turn ignition on, with engine off. Using scan tool, compare ECT and IAT sensor readings. If readings are close to each other, go to step  7 . If readings are not close to each other, go to next step.
  6. Turn ignition off. Disconnect ECT sensor harness connector. Using a DVOM, check resistance between ECT sensor terminals. See appropriate SENSOR OPERATING RANGE CHARTS article. If ECT resistance value is as specified, go to next step. If ECT resistance value is not as specified, go to step  12
  7. Turn ignition on, with engine off. Using scan tool, check ECT sensor value. If scan tool reading is less than - 22°F (- 30°C), go to next step. If scan tool reading is not - 22°F (- 30°C), see DIAGNOSTIC AIDS  .
  8. Using a jumper wire, connect jumper wire between ECT sensor harness connector terminals. If ECT sensor value is greater than 266°F (130°C), go to next step. If scan tool value is not greater than 266°F (130°C), go to step  10 .
  9. Check coolant level and thermostat operation. Repair as necessary. After repairs, go to step  13 . If no problems were found, see DIAGNOSTIC AIDS  .
  10. Turn ignition off. Check for poor connections at ECT sensor and PCM. Repair as necessary. After repairs, go to step  13 . If connectors are okay, go to next step.
  11. If PCM connectors are okay, replace PCM. Program replacement using required equipment. Perform CKP SYSTEM VARIATION LEARN PROCEDURE. See DTC P1336: CKP SYSTEM VARIATION NOT LEARNED  . After repairs, go to step  13 .
  12. Turn ignition off. Replace ECT sensor. After replacing sensor, go to next step.
  13. Using scan tool, clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select SPECIFIC DTC function, and then enter DTC P0125. If scan tool indicates this test ran and passed, go to next step. If scan tool does not indicate this test ran and passed, go to step  2 .
  14. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, system is okay.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.