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 MANUALSCHEVROLET2008CHEVY EXPRESS G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 9 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 4.3L - DTC P0016 TO DTC P0336)DTC P0128CIRCUIT/SYSTEM VERIFICATION
2008 Chevrolet Chevy Express G3500, Van Passenger Extended
Circuit/System Verification
2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Verification
WARNING: This page is about a different variant/trim than selected.
- If the ignition has been OFF for 8 hours or more, the ECT and the IAT, should be within 6°C (11°F) of each other and also the ambient temperature. Turn ON the ignition, with the engine OFF, and use a scan tool to observe the IAT and the ECT sensor parameters.
- Use the scan tool to verify the proper operation of the engine cooling system fans.
- Turn OFF the ignition.
- Inspect the cooling system surge tank for the proper engine coolant level. Refer to Cooling System Leak Testing and Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (Vac N Fill) .
- Verify the proper heat range, and the operation of the thermostat. Refer to Thermostat Diagnosis .
- Operate the vehicle with the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
CAUTION:
Under pressure, the temperature of the solution in the radiator can be considerably higher, without boiling. Removing the radiator cap while the engine is hot (pressure is high), will cause the solution to boil instantaneously, with explosive force. The solution will spew out over the engine, fenders, and the person removing the cap. Serious bodily injury may result. Flammable antifreeze, such as alcohol, is not recommended for use at any time. Flammable antifreeze could cause a serious fire.
IMPORTANT:
A critical analysis of the operation of the thermostat is necessary to properly diagnose these DTCs.
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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.