B0283

DTC B0283

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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 06
- Electric Rear Defrost Circuit Short To Ground or Open

Diagnostic Fault Information






Circuit/System Description

The HVAC control module 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 HVAC control module energizes the rear defog relay.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

The HVAC control module detects a short to ground or open/high resistance in the rear defog relay control circuit for 1 second or greater.

Action Taken When the DTC Sets

* The HVAC control module stores the DTC to memory.
* The rear window defogger will not operate.

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.

Circuit/System Verification

Ignition ON, observe the operation of the defogger grid while pressing and depressing the rear defogger switch. The defogger grid should ACTIVATE and DEACTIVATE when changing between commanded states.

Circuit/System Testing

1. Ignition OFF, disconnect the REAR DEFOG relay.
2. Test for less than 1.0 ohm between the ground circuit terminal 85 and ground.

^ If greater than the specified range, test the relay coil ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 86 and ground.
4. Ignition ON, command the defogger grid ON and OFF by pressing and depressing the rear defogger switch. 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 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 not the specified value, replace the relay.

4. Install a 25-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. Verification Tests

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