The outside rearview mirrors heat during the defrost/defog cycles for the rear window. The heated mirrors are connected to the driver door module (DDM) and the passenger door module (PDM). The DDM and the PDM receive a GMLAN serial data message from the HVAC control module indicating the rear defogger has been activated. The DDM and PDM examine information from the body control module (BCM) to determine if vehicle conditions are correct for the heated mirrors function to be activated. If conditions are correct, the DDM and PDM will command there respective heated mirrors ON.

Battery voltage must be between 9-16 volts.

B1640 01

The DDM or PDM detects a short to voltage on the heating element control circuit.

B1640 02

The DDM or PDM detects a short to ground on the heating element control circuit.

The heated mirror function will be disabled.

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.

Ignition ON, press the rear window defogger switch. The rear window defogger and both heated mirrors should become warm.

Driver

1. Ignition OFF, disconnect the X2 harness connector at the outside rearview mirror.
2. Test for less than 10 ohms between the ground circuit terminal 6 and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 7 and the ground circuit terminal 6.
4. Command the Mirror Heater ON and OFF with a scan tool. 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 DDM.

⇒	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 DDM.

5. If all circuits test normal, test or replace the outside rearview mirror glass.

Passenger

1. Ignition OFF, disconnect the harness connector at the outside rearview mirror.
2. Test for less than 10 ohms between the ground circuit terminal 6 and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 7 and the ground circuit terminal 6.
4. Command the Mirror Heater ON and OFF with a scan tool. 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 PDM.

⇒	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 PDM.

5. If all circuits test normal, test or replace the outside rearview mirror glass.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.