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Home › Hummer › 2008 › H2 4D Utility Pickup › Repair and Diagnosis › Body & Frame › Mirrors › Diagnostic Information and Procedures › DTC B1640 › Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector X3 at the appropriate door switch.
  2. Ignition ON, verify a test lamp does not illuminate between the supply voltage circuit terminal 7 and ground.
    • If the test lamp illuminates, test the supply voltage circuit for a short to voltage.
  3. Ignition OFF, test for infinite resistance between the supply voltage circuit terminal 7 and ground.
    • If less than the specified value, test the supply voltage circuit for a short to ground. If the circuit tests normal, test or replace the applicable rearview mirror face.
  4. Test for 5-10 ohms of resistance between the supply voltage circuit terminal 7 and the low reference circuit terminal 3.
    • If not within the specified range, test the supply voltage circuit and the low reference circuit for an open/high resistance. If the circuits test normal, test or replace the appropriate rearview mirror face.
  5. If all circuits test normal, test or replace the appropriate door switch.
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