GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The body control module (BCM) has a ground at G201. The sole purpose of this ground circuit is to provide a ground for all courtesy lamp current flow through both the theater dim 1 and 2 output circuits.

Conditions for Running the DTC

The input does not match a normal ground potential

Conditions for Setting the DTC

    • The BCM detects a open when a ground is expected.
    • The condition above must be present for more then 0.3 seconds

Action Taken When the DTC Sets

Courtesy lamps will be inoperative.

Conditions for Clearing the DTC

    • A current DTC B2559 will clear if the open is no longer detected by the BCM
    • A history DTC B2559 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present or any other malfunction in the BCM is detected.
    • The BCM receives a clear code command from the scan tool.

Diagnostic Aids

    • If the DTC B2559 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 open in the theater dimming ground circuit
       - The BCM is intermittently opened.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step tests for a open in the ground circuit of the BCM that supplies a ground path for the theater dimming 1 circuit and the theater dimming 2 circuit.

Step

Action

Yes

No

Schematic Reference: Interior Lights Schematics

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Turn ON the ignition, with the engine off.
  2. With the I/P dimmer switch, turn the interior lamps ON.

Do the interior lamps turn ON?

Go to Diagnostic Aids

Go to Step 3

3

Test for an open or high resistance in the ground circuit of the BCM that provides a ground path for the theater dimming 1 and theater dimming 2 circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4

Inspect for poor connections at the harness connector of the body control module]. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 5

5

Important: Perform the set up procedure for the body control module.

Replace the BCM. Refer to Body Control Module Replacement .

Did you complete the replacement?

Go to Step 6

--

6

  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