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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> Accessories & Equipment >> Interior/Illumination Lights >> Lighting >> Diagnostic Information and Procedures >> Park, License, and/or Tail Lamps Malfunction >> Circuit/System Testing

Circuit/System Testing

Park Lamp Switch Circuit Test

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit terminal 8 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Parklamp 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 3A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Parklamp 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 switch.

Park Lamp Relay Circuit Test

  1. Ignition OFF, disconnect the park lamp relay.
  2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate, replace the underhood fuse block.
  3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
    • If the test lamp does not illuminate, replace the underhood fuse block.
  4. Connect a test lamp between the relay control circuit terminal 86 and the B+ circuit terminal 85.
  5. 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 relay control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  6. If all circuits test normal, test or replace the park lamp relay.

Exterior Lamps Circuit Test

  1. Ignition OFF, disconnect the harness connector at an affected park, marker, license, or tail lamp.
  2. Verify that a test lamp illuminates when connected between B+ and the listed ground circuit terminal.
    • Front park lamp terminal 1
    • Rear park lamp terminal A
    • Rear aux park lamp terminal A
    • Side marker lamp terminal B
    • License lamp terminal B
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, connect a test lamp between the listed control circuit terminal and ground.
    • Front park lamp terminal 2
    • Rear park lamp terminal E
    • Rear aux park lamp terminal B
    • Side marker lamp terminal A
    • License lamp terminal A
  4. 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.
  5. If all circuits test normal, test or replace the affected lamp.
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