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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G2500, VAN PASSENGER EXTENDED, 5.0 MREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 133 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L)DIAGNOSTIC TESTSDTC P0125: ENGINE COOLANT TEMPERATURE INSUFFICIENT FOR CLOSED LOOP FUEL CONTROLDIAGNOSTIC PROCEDURES
2001 Chevrolet Chevy Express G2500, Van Passenger Extended, 5.0 M

Diagnostic Procedures

2001 Chevrolet Chevy Express G2500, Van Passenger Extended, 5.0 MSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
  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. NOTE: The cooling fans are commanded ON when certain engine coolant temperature DTCs are set.
  2. Is the cooling system coolant low? If yes, go to drain & refill procedures in appropriate SPECIFICATIONS & DRIVE BELT ROUTING article under COOLING SYSTEM (MECHANICAL). If no, go to next step.
  3. Check and verify the proper operation of the thermostat. For thermostat specifications, see appropriate SPECIFICATIONS & DRIVE BELT ROUTING article under COOLING SYSTEM (MECHANICAL). Did you find and correct the condition? If yes, go to step  14.
  4. Disconnect the ECT sensor harness connector. Inspect for corrosion on the ECT sensor terminals, improper or corroded terminals at the ECT harness connector and loose terminals in the ECT harness connector. Did you find and correct the condition? If yes, go to step  14. If no, go to next step.
  5. Measure the voltage from the signal circuit of the ECT sensor to a good ground using a DMM. Is the voltage 4.8-5.2 volts? If yes, go to next step. If no, go to step  8.
  6. Measure the voltage from the signal circuit of the ECT sensor to the low reference circuit of the ECT sensor using a DMM. Is the voltage 4.8-5.2 volts? If yes, go to step  9. If no, go to next step.
  7. Check the ECT sensor low reference circuit for high resistance. Did you find and correct the condition? If yes, go to step  14. If no, go to step  11.
    8. NOTE: Do not hold the ECT sensor by the probe.
  8. Turn ignition switch to OFF position. Remove the ECT sensor. Place the sensor on a work surface away from any heat source. Allow the sensor to reach the ambient air temperature for 30-60 minutes. Observe and record the ambient air temperature of the vehicle environment using an accurate thermometer. Measure the resistance of the ECT sensor and record the value. Compare the resistance measurement of the ECT sensor to the ambient air temperature on the Temperature vs. Resistance table. See TEMPERATURE VS. RESISTANCE  table. Is the resistance measurement of the ECT sensor within the specified range? If yes, go to step  10. If no, go to step  12.
  9. Check the ECT sensor low reference circuit for a high resistance or an open. Repair circuit as necessary. Did you find and correct the condition? If yes, go to next step. If no, go to  12.
  10. Install the ECT sensor. After installation of ECT sensor is complete, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.
  11. Check for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
  12. Reinstall ECT sensor. After installation, go to step  14.
  13. Replace ECT sensor. After repair, go to next step.
  14. Using scan tool, clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  15. Using the scan tool, observe the CAPTURE INFO. Does the scan tool display any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
RENDER: 1.0x

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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.