GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Malibu 🢒 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 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

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Relay Switch B+

1

1

--

--

Rear Defog Switch Signal

2

1

1

--

Rear Defog Relay Control

B0283 02

B0283 05

B0283 05

--

Rear Window Defogger Grid Control

1

1

2

--

Rear Defog Indicator Control

B0283 02

B0283 05

B0283 05

--

HVAC Ground

--

1

1

--

Relay Coil Ground

--

B0283 05

1

--

Rear Window Defogger Grid Ground

--

1

1

--

1. Rear Defogger Inoperative

2. Rear Defogger Always ON

Circuit/System Description

When the rear defog switch is pressed, a signal is sent to the body control module (BCM) which energizes the rear defog relay by providing a B+ to the control circuit of the rear 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 contains the rear defog switch and also illuminates the rear defog indicator on the switch button, upon this request.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

B0283 02

The BCM detects a short to ground in the relay coil control circuit (RPO C60 and C68) or a short to ground in the defog indicator control circuit (RPO C60).

B0283 05

Will only set when the BCM detects a concurrent short to voltage or an open/high resistance in both of the relay control and the rear defog indicator circuits (RPO C60) or an open/high resistance in the relay coil control circuit (RPO C68).

Action Taken When the DTC Sets

The rear window defogger will not operate

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

Ignition ON, command the Rear Defog Relay ON and OFF with a scan tool. The rear window defogger and rear window defogger indicator should turn ON and OFF when changing between the commanded states.

⇒If the DTC sets on the automatic HVAC system RPO C68, refer to Automatic HVAC.
⇒If the DTC sets on the manual HVAC system RPO C60, refer to Manual HVAC.

Circuit/System Testing

Automatic HVAC

  1. Ignition OFF, disconnect the R/WDO DEFOG relay.
  2. Connect a test lamp between the control circuit terminal 86 and ground.
  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/WDO DEFOG relay.

Manual HVAC

  1. Ignition OFF, disconnect the X1 harness connector at the HVAC control module.
  2. Disconnect the R/WDO DEFOG relay.
  3. Test for less than 1 ohm between the ground circuit terminal 85 and ground.
    4. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Connect a test lamp between the control circuit terminal 86 and ground circuit terminal 85.
  5. 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.
    6. ⇒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.
  6. Ignition OFF, connect the X1 harness connector at the HVAC control module.
  7. Command the rear window defogger ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    8. ⇒If the test lamp does not turn ON and OFF, replace the HVAC control module.
  8. If all circuits test normal, test or replace the R/WDO DEFOG relay.

Component Testing
  1. Ignition OFF, disconnect the R/WDO DEFOG relay.
  2. Test for 60-180 ohms between terminals 85 and 86.
    3. ⇒If 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 30A 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 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 BCM and HVAC replacement, setup, and programming