Chevrolet Silverado / GMC Sierra. Service manual — part 2473

Circuit/System Description

When the PRNDL is placed in the REVERSE position, a signal is sent to the body control
module (BCM). The BCM then applies voltage through the backup lamps relay control circuit to
the BACK/UP lamp relay in the underhood fuse block, inside rearview mirror, and rearview
camera module. The BACK/UP lamp relay then illuminates the backup lamps.

Conditions for Running the DTC

The ignition is ON.

The backup lamps must be commanded ON.

Conditions for Setting the DTC

The BCM detects a short to ground on the backup lamp relay control circuit when the backup
lamps are being commanded ON.

Action Taken When the DTC Sets

The backup lamps do not illuminate.

Conditions for Clearing the DTC

The conditions for setting the DTC are no longer present.

A history DTC clears after 100 malfunction-free ignition cycles.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Circuit Testing

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

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, activate the Backup Lamps output control on the scan tool. The Backup Lamps
parameter in the data list should display On and the backup lamps should illuminate.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector X2 at the BCM.

2. Ignition ON, vehicle in park, verify the backup lamps are not on.

If the backup lamps are on, test the backup lamp relay control circuit terminal 22 for a
short to voltage. If the circuit tests normal replace the underhood fuse block.

3. Install a 10A fused jumper wire between the relay control circuit terminal 22 and battery

voltage. Verify the backup lamps are on.

If the backup lamps are not on, test the backup lamp relay control circuit for an
open/high resistance or short to ground. If the circuit tests normal replace the
underhood fuse block.

4. If all circuits test normal, replace the BCM.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Underhood Electrical Center or Junction Block Replacement

Control Module References for BCM, inside rearview mirror, and rearview camera
module replacement, setup, and programming

DTC B2555

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.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B2555 01

Passenger Compartment Lamp Control Circuit Short to Battery

DTC B2555 02

Passenger Compartment Lamp Control Circuit Short to Ground

Diagnostic Fault Information

Circuit/System Description

When the body control module (BCM) signals for courtesy lamp operation, a message is sent over
the GM LAN serial data circuit to the driver door and passenger door switches. The driver door
switch and passenger door switch the applies battery voltage to the left and right courtesy lamp
control circuits illuminating the door courtesy lamps. The driver door and passenger door
switches also provide ground to the lamps.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

A message is sent from the BCM over the GM LAN serial data circuit to the driver door and
passenger door switches to active the door courtesy lamps.

Conditions for Setting the DTC

B2555 01

This DTC will set when the driver or passenger door switch detects a short to voltage in the
courtesy lamp control circuit.

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Left Courtesy Lamp Control
Circuit

B2555 02

1

B2555 01

-

Right Courtesy Lamp Control
Circuit

B2555 02

1

B2555 01

-

1. Courtesy Lamps Inoperative

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

B2555 02

This DTC will set when the driver or passenger door switch detects a short to ground in the
courtesy lamp control circuit.

Action Taken When the DTC Sets

B2555 01

When this DTC is present, the door courtesy lamps will remain illuminated.

B2555 02

When this DTC is present, the door courtesy lamps will be inoperative.

Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists.

A history DTC will clear once 100 consecutive malfunction-free ignition cycles have
occurred.

Reference Information

Schematic Reference

Interior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Lighting - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado