I have a 2007.5 LMM Sierra. Recently I started getting a DIC message which stated "Service Trailer Brake System." It couldn't have come at a worse time as I just signed the papers on a brand new 5'er and I'm supposed to pick it up this weekend. I have a 7 pin plug with my towing package and when I hook it up to my current travel trailer, everything works except for the trailer brakes. I checked the one 15A fuse under the hood for the brake controller but it is not blown. I put a volt meter on the pin for the trailer brake and it's not getting any juice. That's about the extent of my electrician skills. I started getting the message spontaneously and was not even towing anything when it started. I need to get it working by Friday if possible. Anyone have any ideas? Thanks in advance.