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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 873 (Fixed & MOVEABLE Window Systems) >> Diagnostic Information and Procedures >> DTC B0283 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, remove the REAR DEFOG relay in the underhood fuse block.
  2. Test for less than 1 ohm of resistance between the relay coil ground circuit terminal 85 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the relay coil control circuit terminal 86 and the ground circuit terminal 85.
  4. Ignition ON, operate the rear window defroster ON and OFF. 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 HVAC control module.
    • 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 HVAC control module.
  5. If all circuits test normal, replace the REAR DEFOG relay.
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