GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The BCM controls the following lamps when the IP dimmer switch is ON or any door is opened:

    • The instrument panel courtesy lamp, LH
    • The instrument panel courtesy lamp, RH
    • The inside rear view mirror lamps
    • The cargo lamp
    • The roof rail reading lamp, LH
    • The roof rail reading lamp, RH
    • The sunshade lighted vanity mirror lamps, LH
    • The sunshade lighted vanity mirror lamps, RH

The BCM monitors all but the sunshade lighted vanity mirror lamps for a short to ground or a short to battery positive voltage.

Conditions for Running the DTC

Voltage supplied to the module is in the normal operating range (approximately 10-16 V).

Conditions for Setting the DTC

    • The BCM detects a short to voltage in the courtesy lamps supply voltage circuit of the interior lamps when the dimmer switch is in the ON position or the doors are open.
    • The condition is present for more than 3 ms.

Action Taken When the DTC Sets

The BCM stores DTC B2618 in memory.

Conditions for Clearing the MIL/DTC

    • A current DTC B2618 clears if the BCM no longer detects a short to battery positive voltage.
    • A history DTC B2618 clears after 100 consecutive ignition cycles.
    • The BCM receives the Clear Code commend 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.
    • An intermittent short to voltage in the following locations may cause an intermittent malfunction to occur:
       - The courtesy lamps supply voltage circuit of the interior lamps
       - The BCM

Step

Action

Yes

No

Schematic Reference: Interior Lights Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Turn the ignition to the RUN position.

Do the interior lamps illuminate when the IP dimmer switch is in the ON position?

Go to Diagnostic Aids

Go to Step 3

3

  1. Disconnect the BCM connector C3.
  2. Connect a test lamp between the courtesy lamps supply voltage circuit of the interior lamps at the BCM connector and a ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 5

4

Test for and repair a short to voltage in the courtesy lamps supply voltage circuit of the interior lamps. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

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5

Important: Perform the set up procedure for the body control module (BCM). Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control Systems.

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 6

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6

  1. Use a 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?

System OK

Go to Step 3