GM Service Manual Online
For 1990-2009 cars only

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: Electric Rear Defrost Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Liftgate Module B+

2

2

--

--

Rear Defog Grid Control

B0283

B0283

1

--

Rear Window Defogger Grid Ground

--

2

2

--

1. Rear defogger always ON

2. Rear defogger Inoperative

Circuit/System Description

The liftgate module (LGM) monitors the voltage level on the supply voltage circuit of the rear window defogger. The LGM will test the supply voltage circuit of the rear window defogger every 160 milliseconds. With the rear window defogger inactive, the supply voltage circuit of the rear window defogger will have no voltage present. With the rear window defogger active, the supply voltage circuit of the rear window defogger will be near system voltage.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

    • The LGM detects a short to voltage on the on the rear window defogger control circuit.
    • The LGM detects a short to ground on the on the rear window defogger control circuit..

Action Taken When the DTC Sets

The rear window defogger will malfunction

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

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

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Command the Rear Defog 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 X1 and X2 harness connectors the rear window defogger.
  2. Test for less than 1 ohm between the ground circuit terminal A and ground.
  3. If greater than the specified range, test ground circuit for an open/high resistance.
  4. Connect a test lamp between the control circuit terminal A and ground.
  5. Ignition ON, command the Rear Defog ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  6. 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 LGM.
    If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the LGM.
  7. If all circuits test normal, replace the rear window defogger grid.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Liftgate Window Replacement
    •  Control Module References for LGM replacement, setup, and programming