For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Mirror Heating Element Supply Voltage | B1640 02 | 1 | B1640 01 | --
Low Reference | -- | 1 | 1 | --
1. Heated Mirror Malfunction

### 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

Battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

#### B1640 01

A short to voltage is detected on the mirror heating element supply voltage circuit.

#### B1640 02

A short to ground is detected on the mirror heating element supply voltage circuit when attempting to activate the heated mirror.

### 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

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Outside Mirror Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

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

⇒ | If the rear window defogger is inoperative, refer to Rear Window Defogger Malfunction.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector X1 (RPO W49) or X2 (RPO DNP) at the outside rearview mirror.
2. Wait 1 minute, test for less than 1.0 ohm 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 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 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 door switch.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Outside Rearview Mirror Glass Replacement

• | Control Module References for DDS or PDS replacement, setup and programming