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 Descriptor

DTC B3743 5A: Rear Window Heating Switch Stuck

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Rear Defrost Relay B+ | 2 | 2 | -- | --
Rear Defrost Switch Signal | B3743 5A | 2 | 2 | --
Rear Defog Relay Control | B0283 00 | B0283 00 | B0283 00 | --
Rear Defog Indicator Control | B0969 02 | 3 | B0969 01 | --
Rear Defogger Grid Control | 2 | 2 | 1 | --
Rear Window Defogger Grid Ground | -- | 2 | 2 | --
1. Rear Defogger Always On 2. Rear Defogger Inoperative 3. Rear Defogger Indicator Inoperative

### Circuit/System Description

The instrument panel cluster (IPC) monitors the voltage level in the rear window defogger switch signal circuit. The voltage level should be low when the rear window defogger switch is open and the voltage will be near system voltage when the rear window defogger switch is closed.

### Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

The IPC detects a continuous defog request for greater than 20 minutes.

### Action Taken When the DTC Sets

The rear window defogger will continuously be active.

### 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 DTC.

• | A history DTC will clear after 50 ignition cycles.

### Reference Information

#### Schematic Reference

Defogger Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Rear Window Defogger 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, observe the scan tool Defrost Switch parameter while pressing and depressing the rear window defogger switch. The parameter should change between Active and Inactive.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the HVAC control assembly.
2. Ignition ON, verify the scan tool Defrost Switch parameter is Inactive.

⇒ | If not the specified value, test the signal circuit terminal 12 for a short to voltage. If the circuit tests normal, replace the IPC.

3. Ignition ON, connect a 5A fused jumper wire between the signal circuit terminal 12 and B+. Verify the scan tool Defrost Switch parameter is Active.

⇒ | If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPC.

4. If all circuits test normal, replace the HVAC control assembly.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heater and Air Conditioning Control Replacement

• | Control Module References for IPC replacement, setup, and programming