GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 LaCrosse 🢒 DTC 🢒 DTC B0283

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    •  Strategy Based Diagnosis

DTC Descriptor

DTC B0283: Electric Rear Defrost Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Relay B+ Circuit

2

2

--

--

Rear Defog Relay Control

B0283

B0283

B0283

--

Rear Defogger Control Circuit

2

2

1

--

HVAC Class 2 Serial Data

2

2

2

--

Rear Window Defogger Grid Ground

--

2

2

--

1. Rear defogger always ON

2. Rear defogger inoperative

Circuit/System Description

The body control module (BCM) monitors the voltage level on the supply voltage circuit of the R/DEFOG relay. The voltage level should be low while the R/DEFOG relay is de-energized. The voltage will be near system voltage when the BCM energizes the R/DEFOG relay.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

The DTC will set when the BCM detects a fault in the Rear Defog Relay Control circuit for 1 second or greater.

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
    • 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

Stationary Windows 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

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

Circuit/System Verification

Ignition ON, command the rear window defogger ON and OFF with a scan tool. Observe the rear window defogger operation as the rear window defogger turns ON and OFF.

Circuit/System Testing
  1. Ignition OFF, disconnect the R/DEFOG relay.
  2. Connect a test lamp between terminal J3 and terminal K1.
  3. 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.
    4. ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒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 BCM.
  4. If all circuits test normal, test or replace the R/DEFOG relay.

Component Testing
  1. Ignition OFF, disconnect the R/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 greater than the specified range, replace the relay.
  4. Install a 40-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
    •  HVAC Control Module Programming and Setup
    •  Relay Replacement