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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1111 (Mirror Systems) >> Diagnostic Information and Procedures >> Automatic Day-Night Mirrors Inoperative >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition ON, headlamps ON, vehicle in PARK, cover the front light sensor with a towel or other suitable item. Shine a flashlight at the rear light sensor while observing the inside rearview mirror face. The inside rearview mirror face should dim.
    • If the mirror face does not dim, test or replace the inside rearview mirror.
  2. Headlamps ON, park brake applied, cover the front light sensor with a towel or other suitable item. Shine a flashlight at the rear light sensor while observing the inside rearview mirror face. Place the transmission in REVERSE. The inside rearview mirror face should transition from dim to bright.
    • If the mirror does not transition from dim to bright, refer to Circuit/System Testing for Reverse Input Malfunction.
  3. Headlamps ON, vehicle in PARK, cover the front light sensor with a towel or other suitable item. Shine a flashlight at the rear light sensor while observing the left outside rearview mirror face. The left outside rearview mirror face should dim.
  4. Remove the towel from the inside rearview mirror and remove the flashlight. Verify the inside rearview mirror face returns to its normal bright state.
    • If the mirror face does not return to its normal state, test or replace the inside rearview mirror.
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