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Home >> Hummer >> 2008 >> H3 Base, Automatic >> Repair and Diagnosis >> Accessories & Equipment >> Headlights >> Lighting >> Diagnostic Information and Procedures >> Interior Backlighting Malfunction >> Circuit/System Testing

Circuit/System Testing

Dimmer Switch Circuit Test

  1. Ignition OFF, disconnect the headlamp switch connector.
  2. Verify that a test lamp illuminates between the low reference circuit terminal 3 and B+.
    • 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 inoperative interior backlighting lamp.
  2. Verify that a test lamp illuminates between the listed component ground circuit and B+.
    • Accessory switch terminal 13
    • Hazard switch terminal B
    • HVAC control module terminal C
    • Rear window wiper/washer switch terminal A
    • Radio terminal B5 X1
    • Sunroof switch terminal C
    • Headlamp switch terminal 3
    • If the test lamp does not illuminate, test the ground circuit for a short to voltage or an open/high resistance.
  3. Ignition OFF, park lamps ON, verify that a test lamp illuminates between the listed control circuit terminal and ground.
    • Accessory switch terminal 12
    • Hazard switch terminal A
    • HVAC control module terminal D
    • Rear window wiper/washer switch terminal D
    • Radio terminal B4 X1
    • Sunroof switch terminal B
    • Headlamp switch terminal 6
    • If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the BCM.
    • If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, replace the component with the inoperative backlighting.
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