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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 888 (Mirror System) >> Diagnostic Information and Procedures >> Heated Mirrors Inoperative (without RPO AN3) >> 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, disconnect the harness connector at the outside rearview mirror.
  2. Ignition OFF, test for less than 5 ohms of resistance between the ground circuit terminal 3 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the B+ circuit terminal 7 and ground.
  4. Ignition ON, command the rear window defogger ON and OFF with the rear defogger switch. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the B+ circuit for a short to voltage.
    • If the test lamp is always OFF, test the B+ circuit for a short to ground or an open/high resistance.
  5. If all circuits test normal, test or replace the outside rearview mirror face.
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