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Home >> Hummer >> 2008 >> H3 Base, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 3 (Lighting Systems) >> Diagnostic Information and Procedures >> Interior Backlighting Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Isuzu i-370, 2008 Isuzu i-290, 2008 GMC Canyon, and 2008 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.

Dimmer Switch Circuit Test

  1. Ignition OFF, disconnect the headlamp switch connector.
  2. Ignition OFF, verify that a test lamp illuminates between the low reference circuit terminal 3 and battery voltage.
    • If the test lamp does not illuminate, test the low reference circuit for an open/high resistance.
  3. Ignition ON, verify that the scan tool dimming potentiometer parameter displays greater than 4 volts.
    • If the parameter displays less than the specified value, test the switch signal circuit 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 14 and the low reference circuit terminal 3. Verify the scan tool dimming potentiometer parameter displays less than 1 volt.
    • If the parameter displays greater than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If the circuits test normal test or replace the headlamp switch.

Interior Backlighting Circuit Test

  1. Ignition OFF, disconnect the harness connector at the affected component.
  2. Ignition OFF, verify that a test lamp illuminates between the affected component ground circuit terminal and battery voltage.
    • HVAC control module X1 terminal 14
    • Hazard switch terminal B
    • Accessory switch terminal H
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the affected component backlighting control circuit terminal and ground.
    • HVAC control module X1 terminal 14
    • Hazard switch terminal A
    • Accessory switch terminal G
  4. Ignition ON and parklamps ON, operate the dimmer switch from high to low. The test lamp should illuminate bright to dim when rotating the dimmer switch.
    • If the test lamp is always off, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM.
    • If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the affected component.
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