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
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 Switch Signal | 3 | 2 | 2 | --
Rear Defog Indicator Control | B0283 02 | B0283 05 | B0283 05 | --
Rear Defog Relay Control | B0283 02 | B0283 05 | B0283 05 | --
Rear Window Defogger Grid Control | 1 | 1 | 2 | --
Relay Coil Ground | -- | 1 | 1 | --
Rear Window Defogger Grid Ground | -- | 1 | 1 | --
1. Rear defogger Inoperative 2. Rear Defogger Always ON

### Circuit/System Description

The body control module (BCM) monitors the voltage level on the supply voltage circuit of the REAR DEFOG relay. The voltage level should be low while the REAR DEFOG relay is de-energized. The voltage will be near system voltage when the BCM energizes the REAR DEFOG relay.

### Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

#### B0283 02

The BCM detects a short to ground in the relay coil control circuit or a short to ground in the defog indicator control circuit.

#### B0283 05

Will only set when the BCM detects a concurrent short to voltage or an open/high resistance in both of the relay control and the rear defog indicator circuits.

### Action Taken When the DTC Sets

The rear window defogger will be inoperative.

### 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, command the Rear Defog Relay ON and OFF with a scan tool. The rear window defogger and rear window defogger indicator should turn ON and OFF when changing between the commanded states.

### Circuit/System Testing

1. Ignition OFF, disconnect the X2 harness connector at the HVAC control module.
2. Disconnect the REAR DEFOG relay.
3. Test for less than 1 ohm between the ground circuit terminal 86 and ground.

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

4. Connect a test lamp between the control circuit terminal 85 and ground circuit terminal 86.
5. Ignition ON, command the Rear Defog Relay 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 BCM.

⇒ | 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 BCM.

6. Ignition OFF, connect the X2 harness connector at the HVAC control module.
7. Command the rear window defogger 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 or always OFF, replace the HVAC control module.

8. If all circuits test normal, test or replace the REAR DEFOG relay.

### Component Testing

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

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

4. Install a 40-amp 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 BCM and HVAC control module replacement, setup, and programming