Heated Mirrors Inoperative

Heated Mirrors Inoperative

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)provides an overview of each diagnostic category.

Circuit/System Description

With the ignition in the RUN position, and the rear window defogger switch depressed, a class 2 serial data message is sent from the HVAC control module to the body control module (BCM) requesting rear defog operation. The BCM responds by providing ground to the rear defog control signal circuit energizing the RR defog relay. The RR defog relay then provides voltage to the rear defog element supply voltage circuit and the outside rearview mirror supply voltage circuit operating the rear defog system and the heating elements within the outside rear view mirrors. The HVAC control module illuminates the rear window defogger indicator when a class 2 serial data message is received indicating that the BCM is requesting rear defog operation. The RR defog relay receives battery positive voltage to both the coil and switch input sides from the RR DEFOG fuse in the underhood fuse block. Ground for the outside rear view mirrors is provided at G301 or G302.

When you start the engine and press the rear window defogger switch for the first time, the defogger cycle lasts for 15 minutes. Further operation results in 7.5 minute defogger cycles. The defogger cycle resets to 15 minutes when you cycle the ignition to the OFF position and then back to the ON position.

If battery voltage is low, the BCM will disable the rear window defogger.

Reference Information
Schematic Reference

Outside Rearview Mirror Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Outside Mirror Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)for Scan Tool Information

Circuit/System Verification

Ignition ON, command the rear window defogger ON and OFF with a scan tool. Observe the rear window defogger and heated outside mirror operation as the rear window defogger turns ON and OFF.

If the rear window defogger is inoperative, Refer to Rear Window Defogger Malfunction (Rear Window Defogger Malfunction).

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate outside rearview mirror.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the ground circuit terminal A and ground.

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

3. Ignition ON, connect a test lamp between the control circuit terminal E and ground.
4. Command the rear window defogger 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 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, replace appropriate outside rear view mirror.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Power Mirror Replacement (Power Mirror Replacement)