Check Trailer Brake connection

[Jonathan Yusubov]

On my 2021 sierra 3500 HD he comes up as service trailer brake, There’s nothing wrong with the trailer because I connected it to a friend of mine’s other truck what’s the best way to fix this with anyone knows I would really appreciate it

[unit]

It could be the pigtail on the trailer.  My 2020 2500HD did not like the pigtail on my 2018 Airstream trailer. I changed the pigtail to one with blade type connectors and it solved the problem.  The new pigtail slides into the truck plug easier and makes a more secure connection.  This might not fix your problem but it's inexpensive and worth a try.

 

https://www.amazon.com/NEW-SUN-Connector-Trailer-Adapter/dp/B07HVS1SY3/ref=sr_1_14_sspa?keywords=trailer+pigtail&qid=1642040293&sprefix=trailer+pig%2Caps%2C97&sr=8-14-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExWkgwR1AzMEhXR0tSJmVuY3J5cHRlZElkPUEwMTc4Njg5MVVaU1g2NTZCVERFTSZlbmNyeXB0ZWRBZElkPUEwODU2MzkxM09XWTdKVDFCSklJQSZ3aWRnZXROYW1lPXNwX210ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

[Jonathan Yusubov]

I fixed the pigtail on the trailer already to try and solve this problem it didnt do the trick

[Pfc1]

I have a 20 3500 HD and we pull a 5th wheel. I have had many instances where I've had to plug and un plug because the truck was not recognizing the camper, no trailer connection. But when it does this the lights and brakes do work. Not really sure where the problem is, just another intermittent electrical issue. Also I have had the not recalling brake gain issue as well, but never  had an issue towing or braking