Will be watching this one. I had a plug added in the bed. Brakes all work perfect. At random times without the trailer I get the same message. Wiring was not cut to add the plug. It was added to the harness under front of box. Hope you get it sorted out camio70.

 

Had same problem. Dealership replaced a relay for the brake controller above the rear axle. Didn't fix problem. Took it back to where I had them install the extra trailer plug in the box and found that the GM provided harness wasn't long enough to install the plug where I wanted it. Where they had spliced onto the wires to make them longer had become wet. They remade all the connections and used water proof shrink tube on the individual wires and I haven't had a problem since.

 

My dealer just fixed the same problem. They replaced the EBCM/BPMV assembly, TBCM and the Brake Pressure Sensor. It took them 4 days to figure it out, but they finally managed to clear all the codes.
Barry

 

What are the "EBCM/BPMV assembly" and "TBCM" in English, please.

 

The EBCM/BPMV assembly is the Electronic Brake Control Module / Brake Pressure Modulating Valve assembly. The TBCM is the Trailer Brake Charging Module. You should be able to google these and see what they look like.
Barry

 

I had the same problem but it was an easy fix -

3 weeks ago I bought a new '09 2500D CC. A week later I took it to my buddies Truck accessory shop to have a B&W gooseneck hitch installed, while the truck was there I had them install the RV plug in the bed wall. The shop used a wiring harness which plugs into the trucks wiring harness. A few days after this was done we had heavy rains here and I started getting the message "Service Trailer Brake System". Not knowing if the problem was with the new truck or the aftermarket wiring system, I took the truck to the dealer. Discussed the matter with the Tech. He crawled under the truck and unplugged the aftermarket wiring harness. A few tablespoons of water ran out. The Tech blowed out the connectors and added silicon grease and plugged everything back together. It appears that the aftermarket wiring harness was not waterproof and when the Truck shop installed it he left it hanging down so that water running out of the back of the bed would run into the plug and was causing the problem.

It has been a week now and I have no problems.

Yes I did call my buddy who runs the Truck shop to let him know about the plug, and the importance of having his tech zip tie the plugs up and out of the way so water can not run into the plug.

 

I have the same problem. I had my truck scanned and no codes. then had it scanned with a tech II and it showed 1031 which was a pressure sensor mounted on the side of the M/C

 

Same here, dealer just ordered the pressure sensor. The trailer brakes have never been used to my knowledge, and the truck has 9k miles. Starting to sound like a common problem.

 

i have same issue..just came on one day and it has not got wet. Not even towed.
part number for pressure sensor?

 

I've been having this problem for about 3 months now. Three days ago I had to replace the battery. I had purchased this truck from a man who had replaced the original battery with, I believe , a 35 series battery. I replaced it with the recommended "98" series battery where the positive cable fits over the top of the battery. Since then I have not seen the "service trailer brake system" message. Not only that the truck shifts gears smoother and seems to perform better overall. I really can't understand how the battery could have made such a difference but I'm happy now!

 

I have the same problem but now after replacing the trailer control module my lights will come on on the dash and when they do my wipers don't work