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Discussion Starter #1
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.
 

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Did you install a receptacle in the bed recently connected to the drop between cap and bed? Check your connections if you can, retape if needed. Can you connect up to someone elses trailer right quick and see if it works? You guys have had a lot of rain up there lately and it wouldnt be too out of the question to have gotten moisture in the something. you can also pull the factory plug from the harness at the back and dry it out (i've had water there).
 

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Did you check the 15amp fuse with your meter?? They will sometimes look good but in fact be blown. If it is all good I would start looking from the plug back. Is this the integrated trailer brake or an aftermarket unit?
 

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Once you figure it out please post what it was, I am having the same problem and am trying to figure it out.
 

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Discussion Starter #5
Did you install a receptacle in the bed recently connected to the drop between cap and bed? Check your connections if you can, retape if needed. Can you connect up to someone elses trailer right quick and see if it works? You guys have had a lot of rain up there lately and it wouldnt be too out of the question to have gotten moisture in the something. you can also pull the factory plug from the harness at the back and dry it out (i've had water there).
No, I haven't installed a new receptacle in the bed for the fifth wheel. The RV dealer was going to install one before I pick it up. I assume that I have to have my brake controller working before I bring it in though. I'll have to check the plug for moisture but it's weird because all other functions work (lights, turn signals, etc)

I have 13+ volts at the 15A fuse for the brake controller (Fuse #21 on the chart). Does anyone know if there is another fuse that is involved in this process?
 

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Discussion Starter #6
Did you check the 15amp fuse with your meter?? They will sometimes look good but in fact be blown. If it is all good I would start looking from the plug back. Is this the integrated trailer brake or an aftermarket unit?
Yes...I'm getting good voltage at the fuse. It is the factory integrated controller.
 

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Do you only get the message with the trailer attached? You could have a bad ground to the brakes or a bad magnet.
 

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I got the same message. I went to the dealer and it was covered under warranty. Repair stated see bulletin #2066487. Brake relay fault! relay replaced and all is well with the world again. Good luck.
 

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Guys please search posts before asking questions. I have posted this in the forum several times now. If you need more info on the bulletin please let me know...
 

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Discussion Starter #10
Guys please search posts before asking questions. I have posted this in the forum several times now. If you need more info on the bulletin please let me know...
I did check some other related posts but for some reason didn't find yours. I appreciate the info. I gave the dealer a call yesterday and he said there were no related bulletins or recalls. Hopefully that bulletin # will help my cause since I'm out of warranty. Thanks.
 

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:eek:Tech found service document 2066487. CT "7521," "944," and "945."
Tech replaced brake trailer relay.
This is all the info on my document from the dealer. I hope it helps!
 

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Discussion Starter #12
Truck's been at the dealer all day and they don't have a clue how to fix it! Gotta love it.
 

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Oh dang man that sucks! Thats why I am afraid to take mine to them, I dont want to pay them again just to tell me that something is wrong.

Thanks for that info though, Fire Captain, may help narrow down the possibilities.
 

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Discussion Starter #14
After two days at the GM dealer, they finally broke down and contacted GM Tech Support. It turns out that it was not the Trailer Brake Relay. The problem was the Brake Pressure Sensor at the master cylinder. It was shorted out. The tech actually told the service advisor that it was a pretty common problem but for some reason, GM is not taking care of it. Since my truck is no longer in warranty, it cost me $383.00 !!
 
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