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Another post about the Service Trailer Brake System

276 Views 8 Replies 2 Participants Last post by  REvans1129
Hey all just purchased a 2010 GMC Sierra 1500 SLT All Terrain. Has all the extra towing capabilities with the integrated trailer brake controller. So driving it home yesterday and the Service Trailer Brake System message came on. There is power to the trailer wire plug in. Since there is power I don't think its a fuse issue, but will be double checking that. After reading some forum posts and the interwebs I'm thinking it could be the IBCT switch, or the trailer relay module. I have a trailer brake controller that I installed on a GMC Yukon, but don't plan on using that to tow anymore. Could I install that in the Sierra and use that instead of the ITBC? Or should I just replace the switch and the trailer tow relay module? If I go that route is the relay module under the spare tire or on the frame rail on this vehicle?

Thanks for you help and answers, appreciate it!
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I would suggest diagnosing where the problem is, at least by getting codes from the ITBC, but you need a pretty good code reader to do it (I bought a knockoff MDI usb-obdii passthrough unit, and use Tech2Win on a windows laptop, not that expensive, highly recommended if you plan on keeping your truck for some time and diagnosing/working on it yourself).

Those are common items that fail (particularly the switch through use), but it can be other things. For my '12 3500, it turned out to be that the seal in the connector was catching on the connector housing instead of allowing the housing to slide past it, preventing the connector from fully seating, and I would get that code (also a new-to-me truck).
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Thanks for the advice! I'll post an update when I get it figured out.
But to follow up, which connector and connector housing? Thanks!
Mine was the connector to the ITBC, which is around where the spare tire is mounted (the relay is there as well) on my truck. IDK where it is on the 1500's.
Roger that. On at least the 2010 1500s it is on the left frame rail right in front of the spare tire carrier. I will check that connector when I'm down looking at the module and relay.
One more question also, when I put in a trailer break on a GMC Yukon I had to find the wire and hook it up to the small stud on the front of the fuse box. When I looked at this one, that wire is still taped up and not hooked to that small stud. With an integrated trailer brake controller is that ok if that wire is not connected?
Probably not, but IDK for sure, for your particular situation.

If the trailer is big enough for trailer brakes, it should (IMHO) also have a breakaway battery, so if the trailer becomes detached from the truck, the breakaway battery activates the trailer brakes, and it comes to a stop quickly.

Hooking up that wire (if it's the wire I'm thinking about), will send power to the +12V pin on the 7 way connector, which should be hooked up to the breakaway battery on the trailer, keeping it charged up (assuming the trailer is used regularly.

If it's not hooked up, then you need to remember to charge that breakaway battery some other way, which will be more prone to error, so it may not work when you need it to.
Well yesterday evening I went ahead and replaced the integrated trailer brake controller on the dash, the 30 amp fuse, the trailer brake relay (had to drop the spare to get to it), cleaned the plug, and then went on a couple of drives. No "service trailer brake system" light came on! Thanks for all your help!
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