Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2002SILVERADO 1500 HD, RWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 72 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L)DIAGNOSTIC TESTSDTC P0125: ECT EXCESSIVE TIME TO ENTER CLOSED-LOOP FUEL CONTROLDIAGNOSTIC PROCEDURES
2002 Chevrolet Silverado 1500 HD, RWD
Diagnostic Procedures
2002 Chevrolet Silverado 1500 HD, RWDSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 GMC Sonoma and 2002 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
- Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
- Is the cooling system low on coolant? If yes, check cause of loss of coolant. If no, go to next step.
- Turn ignition off. Disconnect the ECT sensor connector. Refer to Engine Coolant Temperature (ECT) Sensor Replacement. Connect a 3-amp fused jumper wire between the signal circuit and the low reference circuit of the ECT sensor. 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 greater than 280°F (38°C)? If yes, go to step 7. If no, go to next step.
- Turn ignition off. Connect a fused jumper wire between a known-good ground and ECT harness connector terminal "B". Turn ignition on, with engine off. Using scan tool, observe ECT sensor temperature. Does the scan tool indicate that the ECT sensor temperature is greater than 280°F (138°C)? If yes, go to next step. If no, go to step 6.
- Test the ECT sensor reference low circuit for a high resistance or an open. Repair the circuit as necessary. Did you find and correct the condition? If yes, go to step 10. If no, see DIAGNOSTIC AIDS .
- Test the ECT sensor signal circuit for a high resistance or an open. Repair the circuit as necessary. Did you find and correct the condition? If yes, go to step 10. If no, see DIAGNOSTIC AIDS .
- Remove ECT sensor. Suspend ECT sensor and a thermometer in a pan of water. Place pan on a burner or hot plate. Check ECT sensor resistance through the specified range of 50-194°F (10-90°C). Does the resistance and temperature closely match the Temperature-vs-Resistance table? See appropriate SENSOR OPERATING RANGE CHARTS article. If yes, go to next step. If no, go to step 9.
- Reinstall ECT sensor and diagnose or replace thermostat.
- Replace ECT sensor. After replacing sensor, go to next step.
- Clear the DTCs with a 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, go to step 2.
- Observe the stored information in Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, 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.