B1640

DTC B1640

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.



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

DTC B1640 02
- Mirror Heater Circuit Short to Ground




Diagnostic Fault Information






Circuit/System Description

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 module indicating that the rear defrost system is active. The door switch supplies B+ through the mirror heating element control circuit when a request is seen. Ground is applied through the mirror heating low reference circuit.


Conditions for Running the DTC

The heated mirrors are commanded ON


Conditions for Setting the DTC

B1640 01

A short to voltage is detected on the mirror heating element supply voltage circuit while the heated mirrors

B1640 02

A short to ground is detected on the mirror heating element supply voltage circuit while the heated mirrors


Action Taken When the DTC Sets

The affected heated mirror will not be activated.


Conditions for Clearing the DTC

* A current DTC will clear when the fault is no longer present
* A history DTC will clear after 40 malfunction free ignition cycles



Reference Information
Schematic Reference

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

Component Connector End Views (Connector Views)
Description and Operation

Outside Mirror Description and Operation (Outside Mirror 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)


Circuit/System Verification

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


Circuit/System Testing

1. Ignition OFF, disconnect the inline harness connector at the outside rearview mirror.
2. Ignition OFF, test for less than 300 ohms of resistance between the low reference circuit terminal 3 and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the appropriate door module.

3. Connect a test lamp between the control circuit terminal 7 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 appropriate 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 appropriate door module.

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



Repair Instructions

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

* Outside Rearview Mirror Glass Replacement (Outside Rearview Mirror Glass Replacement)
* Control Module References (Programming and Relearning)for DDM or PDM replacement, setup and programming