Diagnostic Instructions

DTC Descriptors

DTC B0283 02: Electric Rear Defrost Circuit Short To Ground

DTC B0283 05: Electric Rear Defrost Circuit Short To Battery or Open

DTC B0283 06: Electric Rear Defrost Circuit Short To Ground or Open

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Relay Switch B+	2	2	--	--
Rear Defogger Relay Control	B0283 02 or B0283 06	B0283 05 or B0283 06	B0283 05	--
Rear Window Defogger Grid Control	2	2	1	--
Relay Coil Ground	--	B0283 05 or B0283 06	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

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

B0283 05

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

B0283 06

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

Action Taken When the DTC Sets

The rear window defogger will be inoperative.

Conditions for Clearing the DTC

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Command the Rear Defog Request 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 Defog Request 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

Relay Test

1. Ignition OFF, disconnect the RR 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.