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 B0283 02: Electric Rear Defrost Circuit Short to Ground or Open
DTC B0283 05: Electric Rear Defrost Circuit Short to Battery or Open

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Relay Switch B+ | 2 | 2 | -- | --
Rear Defog Relay Control | B0283 02 | B0283 02, B0283 05 | B0283 05 | --
Rear Windows Defogger Grid Control | 2 | 2 | 1 | --
Rear Defog Relay Ground | -- | B0283 02, B0283 05 | 2 | --
Rear Window Defogger Grid Ground | -- | 2 | 2 | --
1. Rear Defogger Always On 2. Rear Defogger Inoperative

### Circuit/System Description

The HVAC control module monitors the voltage level on the supply voltage circuit of the RR Defog relay. The voltage level should be low while the RR Defog relay is de-energized. The voltage will be near system voltage when the HVAC control module energizes the RR Defog relay.

### Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

#### B0283 02

When the HVAC control module detects a short to ground or an open/high resistance in the RR-Defog relay coil control circuit for 1 second or greater

#### B0283 05

When the HVAC control module detects a short to battery or an open/high resistance in the RR-Defog relay coil control circuit for 1 second or greater.

### Action Taken When the DTC Sets

The rear window defogger will malfunction.

### 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

Command the Rear Window Demister ON and OFF with the scan tool. The rear window defogger should turn ON and OFF when changing between the commanded states.

### Circuit/System Testing

1. Ignition OFF, disconnect the RR DEFOG relay.
2. Test for less than 1 ohm between the ground circuit terminal 85 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance

3. Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85.
4. Ignition ON, command the Rear Window Demister 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 HVAC control 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 HVAC control module.

5. If all circuits test normal, test or replace the RR DEFOG relay.

### Component Testing

1. Ignition OFF, disconnect the RR DEFOG relay.
2. Test for 60-180 ohms between terminals 85 and 86.

⇒ | If the not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If not the specified value, replace the relay.

4. Install a 25A fused jumper wire between relay terminal 85 and 12V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

⇒ | If greater than the specified range, replace the relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Relay Replacement

Control Module References for HVAC control module replacement, setup, and programming