2016 GMC Sierra 2500HD Service Trailer Brake System/Check Trailer Connection

GMCNuneZ71 · July 22, 2019

So I have been having an issue with my truck towing trailers in the sense that I will randomly lose my running lights or brakes not working and getting the messages Service Trailer Brake System or Check Trailer Connection. I took it to the dealership they said it must be the trailer, however when I connect any trailer to my truck I have the same issue. When I connect those trailers to any other vehicle I have no issues at all which leads me to believe it’s my truck not the trailer. Dealership said to bring it to them when it has the code, yea so you want me to drive loops around your dealership with a trailer until I get the message? Then what? I have read some people say it’s the brake fluid and some say it’s the trailer brake relay (like a $30 fix). Anyways I was just looking to see if anyone else had these exact issues. Thank you!!

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Phil McKramer · July 22, 2019

46 minutes ago, GMCNuneZ71 said:

So I have been having an issue with my truck towing trailers in the sense that I will randomly lose my running lights or brakes not working and getting the messages Service Trailer Brake System or Check Trailer Connection. I took it to the dealership they said it must be the trailer, however when I connect any trailer to my truck I have the same issue. When I connect those trailers to any other vehicle I have no issues at all which leads me to believe it’s my truck not the trailer. Dealership said to bring it to them when it has the code, yea so you want me to drive loops around your dealership with a trailer until I get the message? Then what? I have read some people say it’s the brake fluid and some say it’s the trailer brake relay (like a $30 fix). Anyways I was just looking to see if anyone else had these exact issues. Thank you!!

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Not uncommon at all for the trailer brake relay to get corrosion in colder climates where different types of salts are applied on winter roads. My 14 needed it replaced this past feb.

GMCNuneZ71 · July 24, 2019

I live in California not too cold and not close to the ocean

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Cowpie · August 16, 2019

https://www.amazon.com/gp/product/B00559VPK0/ref=ox_sc_saved_title_6?smid=ATVPDKIKX0DER&psc=1

flattop · September 11, 2019

Check the wires at the connector going into the trailer brake power control module. (its under the spare tire) We just had the same problem on a 2015 Silverado. The wire looked good at the connector, but when we slid the plastic wire protection back, there was an open (corroded) wire about 2" up the harness.

ralanis6 · February 9, 2020

I too have a 2500HD and tow a 5th wheel and would get this warning from time to time. I check the 7 pin connector and move the pins so that the connection will be tighter. This usually takes care of it, but it has come back again maybe due to the movement or the connecting and reconnecting of the plug.

dquest · July 17, 2020

On 2/8/2020 at 11:32 PM, ralanis6 said:

I too have a 2500HD and tow a 5th wheel and would get this warning from time to time. I check the 7 pin connector and move the pins so that the connection will be tighter. This usually takes care of it, but it has come back again maybe due to the movement or the connecting and reconnecting of the plug.

I had this problem on both my 2015 and 2017 2500 HD. Traded the 2015 before fixing but with the 2017 I replaced both the in bed and bumper receptacles. Both occurred around the 60k mark. Now I lightly seat the plug just far enough that the cover catches it and no problems. I found pushing it in more only made it worse.

The both receptacles in the bed were aftermarket and completely sealed.

[email protected] · September 23, 2020

I have 2018 1 ton gmc diesel, trailer brakes keep blowing fuse, and get warning that trailer lights need service, just back from dealer second time in a few week, they just replace fuse and act stupid, Its very dangerous pulling heavy trailer over mountain passes with no trailer brakes, I have 2 trailers and same issue. I plug into my other gmc, no problem, have read, that a new trailer plug system might help, So new truck under warranty?? even plug into truck camper and running lights blow..