B2555

DTC B2555

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptor
DTC B2555 05
- Passenger Compartment Lamp Control Circuit Short to Battery/Open.




Diagnostic Fault Information






Circuit/System Description

The INTERIOR LIGHTS fuse supplies battery voltage to the body control module (BCM). The BCM applies battery voltage to the courtesy reading and dome reading lamps through the courtesy lamp supply voltage circuit. The dome/reading lamps are controlled by a 3 position (OFF, DOOR, ON) switch. When the dome/reading lamp switch is placed in the DOOR position the lamps are controlled by the BCM. When any door is opened, the jam switch contacts close and the BCM receives a door-open input. If the BCM receives a door lock or unlock input the BCM will activate the courtesy lamp supply voltage circuit, providing battery voltage to the dome/reading lamps. The BCM shall provide a Parade Mode feature intended to allow the dimming level of certain vehicle displays to remain bright enough for convenient daylight viewing if the park lamps or headlamps are turned on during daylight conditions. The BCM shall provide a Day/Night Mode Determination feature designed to determine whether the vehicle is operating in ambient light conditions consistent with day or night driving. If the BCM is currently in the Day Mode and the LIGHT input indicates the ambient light level has been continuously below the current DNT (day night transition) for the last 15 seconds (Ambient Light Day - Night Timer calibration), the BCM shall enter the Night Mode of operation. If the BCM is currently in the Night Mode and the LIGHT input indicates the ambient light level has been continuously above the current NDT (night day transition) for the last 30 seconds (Ambient Light Night - Day Timer calibration), the BCM shall enter the Day Mode of operation.


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 activate the door courtesy lamps.



Conditions for Setting the DTC

* DTC B2555 05 will set when the BCM detects a short to voltage in the courtesy lamp control circuit.
* It takes 1 second for the code to set.
* BCM is unable to change pulse width modulated (PWM) backlighting when park lamps are On.
* Park lamps On and Day Night Mode status is equal to Night and Parade Mode status and is Correct or True.
* Park lamps On and Parade Mode status is Incorrect or False.



Action Taken When the DTC Sets

DTC B2555 05 is present, when a open or short to voltage on the courtesy lamp control circuit is present.


Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A scan tool CLEAR DTCs command is issued for that switch module.
* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.



Reference Information
Schematic Reference

Interior Lights Schematics (Interior Lights Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Testing

1. Disconnect the Dome/Reading Lamp assembly terminal B.
2. Connect a test lamp between the courtesy lamp control circuit terminal B of the Dome/Reading Lamps and ground.

• If the test lamp illuminates, locate and repair a short to voltage in the courtesy lamp control circuit.
• If the test lamp does not illuminate, locate and repair a short to ground in the courtesy lamp control circuit.

3. If circuits test OK, replace the BCM.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.


Control Module References (Programming and Relearning) for BCM replacement, setup, and programming