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Home >> Cadillac >> 2007 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1625 (Mirror System) >> Diagnostic Information and Procedures >> DTC B1640 >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the X3 harness connector at the appropriate door module.
  2. Ignition ON, verify a test lamp does not illuminate between the control circuit terminal 7 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Ignition OFF, test for infinite resistance between the control circuit terminal 7 and ground.
    • If less than the specified value, test the control 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 control circuit terminal 7 and the low reference circuit terminal 3.
    • If not within the specified range, test the control 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 door module.
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