Circuit/System Testing

2006 Chevrolet Suburban K2500, 6.0 USECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the series/parallel relay, which is the FAN CNTRL relay.
  2. Connect a 30A fused jumper between the normally-open switch contact terminals at the series/parallel relay connector in order to complete the fan ground circuit. Leave this jumper in place for the remainder of this procedure.
  3. Ignition OFF, disconnect the affected relay.
  4. Verify that a test lamp does not illuminate between B+ and the affected relay control circuit terminal.
  5. Remove the test lamp.
  6. Command the affected relay ON with a scan tool. Verify the scan tool Relay Control Ckt. Short Volts Test Status Parameter is OK.
    • If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  7. Install a 3A fused jumper wire between the control circuit terminal and B+. Command the affected relay ON with a scan tool. Verify the scan tool Relay Control Ckt Short Volts Test Status Parameter is Fault.
    • If not the specified value, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  8. Remove the 3A fused jumper wire.
  9. Connect a 30A fused jumper between the positive voltage terminal at the battery and the fan voltage supply circuit terminal at the affected relay connector and verify fan activation.
    • If the fan does not activate, test the fan voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fan.
  10. Ignition ON, connect a 30A fused jumper between the relay switch voltage supply circuit terminal and the fan voltage supply circuit terminal at the affected relay connector and verify fan activation.
    • If the fan does not activate, test the affected relay switch 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.
  11. Ignition ON, verify that a test lamp illuminates between the affected relay coil voltage supply circuit terminal and ground.
    • If the test lamp does not illuminate, test the affected relay coil 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.
  12. If all circuits and the ECM test normal, replace the affected relay.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
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  • β€’ You are not confident in the next step or safety outcome.