GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Century 🢒 DTC 🢒 DTC B2618

Circuit Description

The body control module (BCM) controls the ground for the courtesy lamps through the courtesy lamp low control circuit. The BCM applies voltage to the courtesy lamps through the courtesy lamps supply voltage circuit. Ground for the courtesy lamps is applied from G201 to the BCM.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2618 Passenger Compartment Dimming 2 Circuit High

Conditions for Running the DTC

The BCM must command the courtesy lamp low control circuit on.

Conditions for Setting the DTC
    • The BCM detects a high when the output should be low in the courtesy lamp low control circuit.
    • The condition above must be present for more than 0.3 seconds.

Action Taken When the DTC Sets

The BCM stores DTC B2618 in memory.

Conditions for Clearing the DTC
    • A current DTC B2618 will clear if the short to battery positive voltage in the courtesy lamp low control circuit is no longer detected by the BCM.
    • A history DTC B2618 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present and no other BCM faults are detected.
    • The BCM receives a clear code command from the scan tool.

Diagnostic Aids
    • If the DTC B2618 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • The following conditions may cause an intermittent malfunction to occur:
       - An intermittent short to battery positive voltage in the courtesy lamp low control circuit.
       - The BCM is intermittently shorted to battery.

Step

Action

Yes

No

Schematic Reference: Interior Lights Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the theater dimming #1 output to ON and OFF.

Do the courtesy lamps turn ON and OFF with each command?

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the body control module (BCM) connectors.
  3. Turn ON the ignition, with the engine OFF.
  4. Using a test lamp connected to ground, probe the courtesy lamp low control circuit of the BCM.

Does the test lamp illuminate?

Go to Step 4

Go to Step 5

4

Repair the short to battery positive voltage in the courtesy lamp low control circuit of the BCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

--

5

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming.

Did you complete the replacement?

Go to Step 6

--

6
  1. Use the scan tool in order to clear the DTC.
  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