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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1320 (Mirror System) >> Diagnostic Information and Procedures >> Heated Mirrors Malfunction (w/o AN3, DL3) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis 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. Test for less than 10 ohms between the ground circuit terminal 3 and ground.
    • If greater than the specified value, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the heater element control circuit terminal 7 and ground.
  4. Ignition ON, operate 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 control circuit for a short to voltage.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.
  5. If all circuits test normal, test or replace the outside rearview mirror glass.
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