B1645

DTC B1640 or B1645

DTC Descriptors
DTC B1640 01
- Mirror Heater Circuit Short to Battery

DTC B1640 02
- Mirror Heater Circuit Short to Ground

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview

Circuit/System Description

The driver door switch (DDS) and passenger door switch (PDS) supply voltage to the outside rearview mirror heater elements upon receipt of a GMLAN message from the body control module (BCM) indicating that the rear defrost system is active. The door switches monitor the heater element control circuits whenever the ignition is ON.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

B1640 01

While the heated mirrors are inactive the heater element control circuit is shorted to voltage.

B1640 02

While the heated mirrors are active the heater element control circuit is shorted to ground.

Action Taken When the DTC Sets

The affected heated mirror will not be activated.

Conditions for Clearing the DTC

* The DTC will be current for as long as the fault is present.
* When the fault is no longer present the DTC will be a history status code.

Circuit/System Testing

1. Disconnect the power mirror connector at the door switch and clear the DTC.
2. Ignition ON, verify that the DTC does not reset when the rear defroster switch is activated.

• If the DTC resets, replace the door switch.

3. Disconnect the mirror face electrical terminals and test the mirror heater control circuit for a short to voltage or ground.
4. If the circuits test normal, replace the mirror face.

Repair Instructions

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

* Mirror Face Replacement
* Driver or passenger door lock and side window switch replacement.