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Home › GMC › 2007 › Acadia SLE, FWD › Repair and Diagnosis › Body & Frame › Mirrors › Mirror System › Diagnostic Information and Procedures › DTC B1640 › Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector X1 (RPO DS3) or X2 at the outside rearview mirror.
  2. Ignition OFF, test for less than 300 ohms of resistance between the low reference circuit terminal 3 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the appropriate door switch.
  3. Connect a test lamp between the control circuit terminal 7 and ground.
  4. Ignition ON, command the mirror heater ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the appropriate door switch.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the appropriate door switch.
  5. If all circuits test normal, test or replace the outside rearview mirror face.
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