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HOMESERVICE MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 2013 (ENGINE COOLING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESCOOLING FAN INOPERATIVE (WITHOUT HP2)CIRCUIT/SYSTEM TESTING
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2

Circuit/System Testing

2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2011 GMC Yukon XL, 2011 GMC Yukon, 2011 Chevrolet Tahoe, 2011 Chevrolet Suburban, and 2011 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:

You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Ignition OFF, disconnect the cooling fan relays.
  2. Connect a 30 A fused jumper between the Fan Control relay switch circuit terminal 30 and the relay ground circuit terminal 87. This will complete the left side fan ground circuit. Leave this jumper in place for the remainder of this procedure.
    3. NOTE:

    The following test must be performed on both the high speed fan relay circuit and the low speed fan relay circuit.

  3. Ignition ON, verify that a test lamp illuminates between ground and the relay switched ignition circuit terminal listed below:
    • Fan Low Relay terminal 30
    • Fan High Relay terminal 30
    • If the test lamp does not illuminate, test the appropriate relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the appropriate G10 cooling fan.
    4. NOTE:

    The following test must be performed first on the high speed fan relay circuit and next on the low speed fan relay circuit. Leave the jumper connected to the low speed fan relay circuit for the next test.

  4. Connect a 30 A fused jumper between the cooling fan relay circuit terminals listed below:
    • Fan High Relay terminals 87 and 30
    • Fan Low Relay terminals 87 and 30

      Verify the appropriate fan is activated.

    • If the corresponding cooling fan does not activate, test the relay controlled output circuit and the cooling fan ground circuit for an open/high resistance. If the circuits tests normal, test or replace the appropriate G10 cooling fan.
    • If the corresponding cooling fan activates, replace the appropriate cooling fan relay.
  5. Install the Fan Control Relay. Verify both fans activate at low speed.
    • If both fans do not activate, test the Fan Control Relay switched output circuit terminal 87A for a short to ground or an open/high resistance.
  6. If all the circuits test normal, test or replace the Fan Control 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.