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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 439 (Lighting System) >> Diagnostic Information and Procedures >> Daytime Running Lamps Malfunction (With T4Q) >> Circuit/System Testing

Circuit/System Testing

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Daytime Running Lamp Malfunction

  1. Ignition OFF, disconnect the harness connector at the DRL resistor.
  2. Connect a test lamp between the control circuit terminal C 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 harness connector at the DRL resistor.
  5. Disconnect the harness connector at the appropriate headlamp assembly.
  6. Connect a test lamp between the signal circuit terminal D and B+.
  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 signal circuit for a short to ground. If the circuit tests normal, replace the DRL resistor.
    • If the test lamp is always OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the DRL resistor.
  8. Connect a test lamp between the signal circuit terminal B and B+.
  9. 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 signal circuit for a short to ground. If the circuit tests normal, replace the DRL resistor.
    • If the test lamp is always OFF, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the DRL resistor.
  10. If all circuits test normal, replace the headlamp assembly.

Ambient Light Sensor Malfunction

  1. Ignition OFF, disconnect the harness connector at the ambient light sensor.
  2. Ignition OFF, test for less than 5 Ω between the ground circuit terminal listed below and ground.
    • Terminal C (with CJ2)
    • Terminal B (without CJ2)
    • If greater than the specific range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.65 V.
    • If less than the specified range, test the signal circuit terminal for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a 3 A fused jumper wire between the signal circuit terminal listed below and the ground circuit terminal. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 V.
    • Terminal D (with CJ2)
    • Terminal A (without CJ2)
    • If greater than the specified range, test the signal circuit for a short to voltage 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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