Traction Control Fault and No Trailer Brakes with Brake Controller Installed in 2005 Buick Terraza

Updated 03/22/2016 | Published 03/21/2016

Question:

I have a 2005 Buick Terraza with the Prodigy 2 brake Controller installed. The brake controller does not show any error indicator in the display. I have two issues going on. 1 The van display indicates that there is a traction control fault when I have the trailer connected and press the brake pedal. When I remove the trailer and restart the van, all error messages go away. 2 When I press the brake, I get no indication that the controller is braking the trailer. But when I hit the manual brake lever on the Prodigy, I can get the trailer brakes to operate. I do not get a reading number in the display…. And I don’t “feel” it working until I hit the manual lever…… BUT…. The device does not show any error message…… everything looks fine on the Prodigy…. Could my problem number one and my problem number two be related? Thank you!

asked by: Tyler L

Expert Reply:

There is a special circumstance with brake controller installations on the 2005 Buick Terraza. You have to attach the brake controller red wire to a wire at the BCM (body control module) rather than using the wire on the cold side of the brake switch.

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 effect on the BCM according to GM.

The signal for the Red wire 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.

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 "VCBM" , and 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.

The white wire is in pin location 30. This wire will have 2.5 volts with the ignition in the run position, even though the brake pedal is not applied, and will go to 12 volts when applying the brake pedal.

expert reply by: Michael H