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Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Daytime Running Lamps Malfunction

  1. Ignition OFF, disconnect the X4 harness connector at the underhood fuse block.
  2. Connect a test lamp between the control circuit terminal H4 and B+.
  3. Command the DRL ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Ignition OFF, connect the X4 harness connector at the underhood fuse block.
  5. Remove the DRL 2 fuse from the underhood fuse block.
  6. Connect a test lamp between the relay control circuit of the DRL 2 fuse and ground.
  7. Command the DRL ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit terminal A3 X1 for a short to voltage. If the circuit tests normal, replace the underhood fuse block.
    • If the test lamp is always OFF, test the control circuit terminal A3 X1 for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  8. If all circuits test normal, replace the underhood fuse block.

Ambient Light Sensor Malfunction

  1. Ignition OFF, disconnect the harness connector at the ambient light sensor.
  2. Ignition OFF, scan tool OFF, doors CLOSED, test for less than 5.0 Ω between the ground circuit terminal listed below and ground.
    • Terminal B - (C67/C42)
    • Terminal C - (CJ2)
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.5 V.
    • If less than the specified range, test the signal circuit terminal listed below for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
      • Terminal A - (C67/C42)
      • Terminal D - (CJ2)
  4. Install a 3 A fused jumper wire between the signal circuit terminal listed below and ground. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 V.
    • Terminal A - (C67/C42)
    • Terminal D - (CJ2)
    • If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM
  5. If all circuits test normal, replace the ambient light sensor.
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