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B0283



DTC B0283

Diagnostic Instructions

* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) 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/System Description

Battery positive voltage is supplied through the underhood fuse block to the defog relay switched input. When the rear defog switch button is pressed, the HVAC control module energizes the defog relay by providing a B+ to the control circuit of the defog relay. This allows battery positive voltage from the relay switched input through the switch contacts and out the relay switched output to the rear window defogger grid. The HVAC control module houses the rear defog switch and also illuminates the rear defog indicator on the switch button, upon this request. Ground for the rear window defogger grid is provided by G401 .


When you start the engine and press the rear defog switch button, the defog cycle lasts for 10 minutes. Further operation will result in 5-minute defog cycles.


The rear defogger feature will not time out if vehicle speed is above 48 km/h (30 mph).


If battery voltage is low, the rear defogger feature will be disabled.


Conditions for Running the DTC

The system voltage must be between 9-16 volts.


Conditions for Setting the DTC

B0283 02

This DTC will set when the BCM detects a short to ground in the rear defog relay control circuit .

B0283 05

This DTC will set when the BCM detects a short to voltage or an open/high resistance in the rear defog relay control circuit.


Action Taken When the DTC Sets

* The BCM stores the DTC to memory.
* The rear window defogger will not operate



Conditions for Clearing the DTC

A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.


Reference Information
Schematic Reference

Defogger Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views) for Component Connector End Views
Description and Operation

Rear Window Defogger Description and Operation (Rear Window Defogger Description and Operation)
Electrical Information Reference

* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Circuit Testing (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for Scan Tool Information


Circuit/System Verification

Command the rear window defogger ON and OFF with the scan tool. The rear window defogger and defogger indicator should turn ON and OFF when changing between the commanded states.


Circuit/System Testing


Rear Defogger Malfunction
1. Ignition OFF, disconnect the DEFOG relay.
2. Test for less than 1 ohm of resistance between the relay coil ground circuit 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 rear defogger relay control circuit and the relay coil ground circuit.
4. 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 rear defogger relay 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 rear defogger relay 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 DEFOG relay.



Component Testing


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

If the resistance is 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 of resistance between terminals 30 and 87.

If greater than the specified range, replace the relay.




Repair Instructions

Perform theDiagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Heater and Air Conditioning Control Replacement (Service and Repair)
* HVAC Control Module Replacement (HVAC - Manual)