B1640

DTC B1640

Diagnostic Instructions

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

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 harness connector X1 (RPO DS3) or X2 (RPO DNP) 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 switch.

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 switch.
^ 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 switch.

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

Repair Instructions

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

* Outside Rearview Mirror Glass Replacement