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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> Accessories & Equipment >> Interior/Illumination Lights >> Lighting >> Diagnostic Information and Procedures >> DTC B257A >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Ignition ON, verify the scan tool headlamp switch parameter is inactive.
    • If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the BCM.
  3. Install a 3A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 8. Verify the scan tool park lamp switch parameter is active.
    • If not the specified value, test the park lamp switch signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, test or replace the headlamp switch.
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