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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 Z88, Z75, and Z88) >> Circuit/System Testing

Circuit/System Testing

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Daytime Running Lamp Malfunction - with X88/Z88 and Z75 without T4Q

  1. Ignition OFF, disconnect the X4 harness connector at the BCM.
  2. Ignition ON, verify a test lamp illuminates between the relay control circuit terminal 23 and ground.
    • If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  3. Ignition OFF, reconnect the X4 harness connector at the BCM.
  4. Disconnect the X4 harness connector at the underhood fuse block.
  5. Ignition ON, verify a test lamp does not illuminate between the relay control circuit terminal H4 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  6. Ignition OFF, reconnect the X4 harness connector at the underhood fuse block.
  7. Disconnect the harness connector at the appropriate daytime running lamp.
  8. Test for less then 5 Ω between the ground circuit listed below and ground.
    • Terminal B (Z75)
    • Terminal C (X88/Z88)
      • If less than the specified range, test the ground circuit for an open/high resistance.
  9. Ignition OFF, connect a test lamp between the control circuit terminal A and ground.
  10. Ignition ON, command the DRL ON and OFF with a scan tool. The test lamp should turn ON and OFF.
    • If the test lamp is always ON, test the control circuit 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 for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  11. If all circuits test normal, replace the appropriate daytime running lamp.

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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