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 12 volts. 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