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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 297 (Lighting System) >> Diagnostic Information and Procedures >> Park, License, and/or Tail Lamps Malfunction (Front LED Park/Marker Lamps with T4Q) >> Circuit/System Testing

Circuit/System Testing

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Park Lamp Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer switch.
  2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 8.
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Park Lamp Switch parameter is Inactive.
    • If not the specified value, test the signal circuit terminal 2 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 2 and ground. Verify the scan tool Park Lamp Switch parameter is Active.
    • If not the specified value, test the signal circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the headlamp and panel dimmer switch.

Park, License, and/or Tail Lamps Malfunction

  1. Ignition OFF, disconnect the park lamp relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the park lamp relay.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Disconnect the harness connector at the appropriate park/license/marker lamp.
  6. Ignition OFF, exterior lamps OFF, test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground.
    • Headlamp - Left or Right terminal J
    • Tail Lamp Circuit Board - Left or Right Rear terminal D - with Z75 + E52
    • License lamp terminal B
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the park/license/marker lamp.
  8. Connect a 15 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the park/marker lamps illuminate.
    • If the park/marker lamps do not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the park/license/marker lamp.
  9. Connect a test lamp between the control circuit terminal 85 and B+ circuit terminal 86.
  10. Command the Parking Lamps 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.
  11. If all circuits test normal, test or replace the park lamp relay.

Front LED Park Lamps Malfunction

  1. Ignition OFF, disconnect the PRK LAMP relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the park lamp relay.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  5. Disconnect the harness connector at the inoperative headlamp/park lamp assembly.
  6. Ignition OFF, exterior lamps OFF, test for less than 5 Ω between the ground circuit terminal J and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the inoperative headlamp/park lamp assembly.
  8. Connect a 20 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the marker lamps illuminate.
    • If all of the front park/marker lamp LEDs do not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the headlamp control module.
    • If some of the front park/marker lamp LEDs illuminate, replace the appropriate headlamp assembly.
  9. Connect a test lamp between the control circuit terminal 85 and B+ circuit terminal 86.
  10. Command the Park Lamps 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.
  11. If all circuits test normal, test or replace the park lamp relay.
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