Brake Control Connection Can Shut Down Brake Light System

Technical Bulletin

Problem with Brake Control Installation in 2005-2007 Chevrolet Uplander, Pontiac SV6, Buick Terraza and Saturn Relay

SUMMARY: Connecting a brake control system in these vehicles in a certain way will shut down the brake light system.

PROBLEM: These vehicles use a multiplex system in their wiring. If you connect a brake control to the "cold side" of the brake light switch, it will shut down the brake light system.

SOLUTION: The brake light switch sends an input to the Body Control Module (BCM), which activates the high mount stop lamp. The wire that operates the high mount stop lamp can be used to activate the brake control. Connecting to this wire will not have any effects on the BCM, according to GM. The signal for the Red wire (on the brake controller) can be obtained at the BCM. The BCM is located just under the front of the dash on the left side, just above your left knee as you are seated in the driver's seat.

Custom Fit Brake Controller

Brake Controller Mechanism Viewed from the Floor Image

Fig. 1. BCM as seen from the floor, looking up under the dash. On the very bottom of the BCM you will find a 52-pin connector. The label on the bottom can identify the BCM. On this label will be the acronym VBCM. The 52-pin connector will have a Green locking clip. In the center of this 52-pin connector you will find a White wire. This wire is the high mount brake light wire.

52-pin connector with green locking clip and white wire Image

Fig. 2. The 52-pin connector, green locking clip and white wire on BCM. This White wire is in Pin Location 30. This wire will have 2.5 volts with the key in the "run" position, even though the brake pedal is not applied, and will go to 12 volts when the brake pedal is applied.

Fig. 3. BCM with 52-pin connector on bottom, green locking clip.

Manufacturer: Cequent

Bulletin Date: 7/21/05

Bulletin Number: 09-0110

Updated By: Dani S.

Last Updated: 3/8/2021

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