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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 512 (ENGINE COOLING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P0480CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Passenger Extended

Circuit/System Testing

2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2009 GMC Savana Special, 2009 GMC Savana Camper Special, 2009 GMC Savana, 2009 Chevrolet RV Cutaway, and 2009 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the fan relay.
  2. Measure between the fan relay ground circuit terminal K9 and ground for less than 3 ohms.
    • If more than the specified range, test the ground circuit for an open/high resistance.
  3. Operate the engine at 1,500 RPM for 2 minutes. The fan should be quiet to indicate the clutch is disengaged.
    • If not disengaged, test the cooling fan clutch supply voltage circuit for a short to voltage. If the circuit tests normal, replace the clutch.
  4. Ignition OFF, install a 10A fused jumper wire between the positive terminal at the battery and the cooling fan clutch supply voltage circuit terminal B.
  5. Operate the engine at 1,500 RPM for 2 minutes. The fan should be loud to indicate the clutch is engaged.
    • If not engaged, test the cooling fan clutch supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, test the fan clutch ground circuit for an open/high resistance. If the circuits test normal, replace the clutch.
  6. Operate the engine at 1,500 RPM for 2 minutes. The fan should be loud to indicate the clutch is engaged.
    • If not engaged, test the cooling fan clutch supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the clutch.
  7. Ignition OFF, install a 10A fused jumper wire between the relay voltage supply circuit terminal J12 and the cooling fan clutch supply voltage circuit terminal.
  8. Operate the engine at 1,500 RPM for 2 minutes. The fan should be loud to indicate the clutch is engaged.
    • If not engaged, test the relay voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all connected components and replace as necessary.
  9. Connect a test lamp between the positive terminal at the battery and the cooling fan clutch relay control circuit terminal L12.
  10. Engine RUNNING at 1,500 RPM, command the cooling fan clutch to 80 percent for 2 minutes. The test lamp should turn on steady or flash, indicating that the ECM can control the relay.
    • If the lamp does not flash or vary correctly, test the cooling fan clutch control circuit for a short to ground, a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.
  11. If all circuits and the ECM test normal, replace the relay.
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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.