GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 DTS 🢒 Body Systems 🢒 Fixed and Moveable Windows 🢒 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 Descriptor

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

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

This DTC will set when the BCM detects a short to battery or open/high resistance in the DEFOG relay coil 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
    • This DTC will change from current to history when the fault is no longer present.
    • A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
    • The technician issues a scan tool CLEAR DTCs command.

Reference Information

Schematic Reference

Defogger Schematics

Connector End View Reference

Window Systems Connector End Views

Description and Operation

Rear Window Defogger Description and Operation

Electrical Information Reference

    •  Testing for Intermittent Conditions and Poor Connections
    •  Circuit Testing
    •  Wiring Repairs
    •  Connector Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Circuit/System Verification

Command the rear window defogger 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. Ignition OFF, test for less than 1.0 ohm of resistance between terminal 11 and ground.
    3. ⇒If greater than the specified range, test the relay coil ground circuit for an open/high resistance.
  3. Connect a test lamp between terminal 15 and terminal 11.
  4. Ignition ON, command the Rear Defogger Grid ON and OFF by pressing the Rear Defogger Switch. The test lamp should turn ON and OFF when changing between the commanded states.
    5. ⇒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 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 of resistance between terminals 85 and 86.
    3. ⇒If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals:
    4. • 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.
    5. ⇒If greater than the specified range, replace the relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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