The heated mirrors are connected to the DDM and PDM. The DDM and the PDM receive a GMLAN serial data message from the HVAC control module indicating that the rear window defogger switch has been activated. If conditions are correct, the DDM and PDM will apply battery voltage to the outside rearview mirror heating element control circuits, and ground to the low reference circuits.

Schematic Reference

Outside Rearview Mirror Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Outside Mirror Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information.

1. Ignition ON, press the rear window defogger switch. Verify the rear window defogger indicator illuminates.

⇒	If the rear window defogger indicator does not illuminate, refer to Rear Window Defogger Malfunction.

2. Verify both the left and right outside mirror glass become warm.

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 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 rearview mirror face.

5. If all circuits test normal, test or replace the door module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.