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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 >> DTC B2600 (With T4Q) >> Circuit/System Testing

Circuit/System Testing

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  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 inoperative 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 appropriate headlamp.
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