GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Envoy - 2WD 🢒 Body Systems 🢒 Lighting 🢒 DTC B2550

Circuit Description

When the Body Control Module (BCM) receives a class 2 message from the Powertrain Control Module (PCM) requesting to illuminate the backup lamps, battery voltage is sent directly from the BCM through the backup lamp supply voltage circuit to the backup lamps.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2550 Backup Lamps Control Circuit

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC
    • When the BCM receives a backup lamp request signal and the backup lamp supply voltage circuit is shorted to ground.
    • When the BCM is not receiving a backup lamp request signal and the backup lamp supply voltage circuit is open or shorted to voltage.

Action Taken When the DTC Sets

The backup lamps will not operate.

Conditions for Clearing the MIL/DTC
    • This DTC will clear on current status after the condition for setting the fault is corrected.
    • A history DTC will clear after 100 consecutive ignition cycles without a fault present.
    • History and current DTCs can be cleared using a scan tool.

Diagnostic Aids

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

  1. This step determines if the problem exists in the wiring or the BCM.

    2.

  2. Inspects for poor connections before a component is replaced.

    3.

  3. After replacement of the BCM you must calibrate the new module for proper operation.

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Lighting Systems Connector End Views or Data Communication Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Test the following circuits as indicated. Refer to Circuit Testing and Wiring Repairs .

    • The backup lamp voltage supply circuit for an open, high resistance, short to voltage or short to ground
    • The backup lamp ground circuit for an open or high resistance

Did you find and correct the condition?

Go to Step 5

Go to Step 3

3

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 5

Go to Step 4

4

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

Did you complete the replacement?

Go to Step 5

--

5
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK