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Home >> Hummer >> 2009 >> H3 Base, Automatic >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Headlights >> Lighting System >> Diagnostic Information and Procedures >> Interior Backlighting Malfunction >> Circuit/System Testing >> Dimmer Switch Circuit Test

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.
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