The driver door module (DDM) and passenger door module (PDM) supply voltage to the outside rearview mirror heater elements upon receipt of a serial data message from the HVAC control module indicating that the rear defrost system is active. The door module supplies B+ through the driver/passenger mirror heating element control circuit when a request is seen. Ground is applied through the driver/passenger mirror heating element ground circuit.

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 X1 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 range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the door module.

3. Connect a test lamp between the control circuit terminal 4 and ground.
4. Ignition ON, 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 door module.

⇒	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 door module.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.