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 Defog Relay Control	B0283 02*, B0283 06**	B0283 05*, B0283 06**	B0283 05*	--
Rear Window Defogger Grid Control	2	2	1	--
Rear Defog Relay Ground	--	B0283 05*, B0283 06**	2	--
Rear Window Defogger Grid Ground	--	2	2	--
*Manual HVAC Control Module ** Automatic HVAC Control Module 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 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

B0283 02

The HVAC control module detects a short to ground in the rear defog relay control circuit for greater than 1 second.

B0283 05

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

B0283 06

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 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 REAR 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 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

Relay Test

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 30A fused jumper wire between relay terminal 85 and 12V. 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.