GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra Classic - 4WD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B0283

Circuit Description

The body control module (BCM) monitors the voltage level on the control circuit of the DEFOG relay. The voltage level should be near system voltage while the DEFOG relay is de-energized. The voltage will be pulled low when the BCM energizes the DEFOG relay. The BCM tests the control circuit of the DEFOG relay every 125 milliseconds.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B0283 Electric Rear Defrost Circuit

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

One of the following conditions will cause this DTC to set:

    • The BCM detects a high voltage level on the control circuit of the DEFOG relay, while the relay is energized.
    • The BCM detects a low voltage level or an open on the control circuit of the DEFOG relay, while the relay is not energized.

Conditions for Clearing the DTC
    • A current DTC clears when the malfunction is no longer present.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for voltage at the coil side of the DEFOG relay. The HVAC fuse supplies power to the coil side of the DEFOG relay.

    2.

  2. This step verifies that the BCM is providing ground to the DEFOG relay.

    3.

  3. This step tests if ground is constantly being applied to the DEFOG relay.

    4.

  4. This step tests for an open on the control circuit of the DEFOG relay.

Step

Action

Yes

No

Schematic Reference: Defogger Schematics

Connector End View Reference: Window Systems Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn OFF the ignition.
  2. Disconnect the DEFOG relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition voltage circuit of the DEFOG relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 3

Go to Step 9

3

  1. Connect a test lamp between the control circuit of the DEFOG relay and the ignition voltage circuit of the DEFOG relay coil.
  2. With a scan tool, command the DEFOG relay ON and OFF .

Does the test lamp turn ON and OFF with each command?

Go to Step 7

Go to Step 4

4

Does the test lamp remain illuminated with each command?

Go to Step 6

Go to Step 5

5

Test the control circuit of the DEFOG relay for an open or a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 8

6

Test the control circuit of the DEFOG relay for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 8

7

Inspect for poor connections at the DEFOG relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 10

8

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 11

9

Repair an open or high resistance in ignition voltage circuit of the DEFOG relay coil. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 12

--

10

Replace the DEFOG relay.

Did you complete the replacement?

Go to Step 12

--

11

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Setting the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK