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DTC B0283

DTC B0283

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
Rear Window Defogger Relay Switch B+ 1 1 - -
Rear Window Defogger Relay Control B0283 02 B0283 05 B0283 05 -
Rear Window Defogger Relay Coil Ground - 1 - -
1. Rear Defogger Inoperative


Circuit/System Description

When the HVAC control module receives a rear window defog request from the HVAC control faceplate, the HVAC control module will supply voltage to the relay coil. Battery positive voltage is supplied at all times to the relay switched input and the relay coil is always grounded. This allows battery positive voltage from the relay switched input to flow through the switch contacts and out the relay switched output to the rear window defogger grid.

Conditions for Running the DTC

Battery voltage must be between 9-16 V.

Conditions for Setting the DTC

B0283 02

The HVAC control module detects a short to ground in the relay control circuit.

B0283 05

The HVAC control module detects a short to voltage or an open/high resistance in the relay control circuit.

Action Taken When the DTC Sets


• If B0283 02 is current, the rear window defogger grid will operate continuously.

• If B0283 05 is current, the rear window defogger grid 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

Engine running, command the rear defogger grid ON and OFF by pressing and depressing the heated rear window switch. The rear defogger grid should turn ON and OFF when changing between the commanded states.

Circuit/System Testing


1. Ignition OFF, disconnect the KR5 rear defogger relay.

2. Test for less than 30 Ω between the ground circuit terminal 86 and ground.

3. 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 the ground circuit terminal 86.

5. Engine running, command the rear defogger grid ON and OFF by pressing and depressing the heated rear window switch. The test lamp should turn ON and OFF when changing between the commanded states.

6. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K33 HVAC Control Module.

7. 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 K33 HVAC Control Module.

8. If all circuits test normal, test or replace the KR5 rear defogger relay.


Component Testing


Relay Test

1. Ignition OFF, disconnect the KR5 rear defogger relay.

2. Test for 60-180 Ω between terminals 85 and 86.

3. If not within the specified range, replace the KR5 rear defogger relay.

4. Test for infinite resistance between the following terminals:

• 30 and 86

• 30 and 87

• 30 and 85

• 85 and 87

5. If not the specified value, replace the KR5 rear defogger relay.

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

7. If greater than the specified range, replace the KR5 rear defogger relay.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)

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