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Trailer wiring - The Answer!

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.boB

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2020 Z71 LB 4x4
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Discussion starter · #1 ·
OK this is a strange one that I've never heard of. Coming back from the race track yesterday, towing my car trailer. The dash dings a few times, and "Check Trailer Wiring" shows up in the center of the dash. It easily resets, and immediately says, "trailer connected". This occurs every 5-10 minutes the rest of the drive.

This happens randomly and I can't relate it to speed, turn signal use, or road condition. it started while driving down the highway, not using the brakes.

I used to have a 2016 Colorado with the factory tow package. It developed the same problem, and became more and more frequent. Like every 2-4 minutes. Incredibly annoying. I "fixed" it by disconnecting the brake wire in the 7-way connector. Then I traded it in on my current 2020 Colorado Z71, and the problem disappeared. Until yesterday.

I had a trailer shop check over all the wiring, and all seems well.

Has anyone else had this problem? Is it a BCM? Or maybe the in-dash brake control module?
 
#2 ·
I've had this happen a couple of times but only with one trailer, chances are the trailer has a bad/corroded/loose connection in the trailer brake circuit that intermittently goes open. This happened with our most recent travel trailer on our way back from Oregon last October when it was raining and I had just stopped for fuel. Fiddled with the wiring but not sure what "fixed" it and it was fine for the rest of the trip. Same thing happened with the same trailer earlier this year when I went to test the trailer brakes, instead of activating it threw the message up on the dash. I called it a name, kept driving, and it went away and hasn't come back.

Never had any problems with any other trailers and we just got back from a 2,500 mile-ish road trip towing our off-road tear drop (including rough roads, paved and unpaved), and never had any hiccups.

The trailer shop may not have found anything because the circuits were testing good at the time. I'd start by tracing the trailer brake wire as far as you can and inspect any splices, etc, as well as the pigtail junction box on the trailer to see if anything is loose.
 
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#3 ·
Try shutting off your Cruise Control. Unplug trailer. Turn engine off, plug trailer back in and see if that works. Sounds crazy but worked for me on my truck. Some thing about fuses. From that point on I was able to use Cruise Control and never had a problem.
 
#4 ·
24Travel said:
Try shutting off your Cruise Control. Unplug trailer. Turn engine off, plug trailer back in and see if that works. Sounds crazy but worked for me on my truck. Some thing about fuses. From that point on I was able to use Cruise Control and never had a problem.
Click to expand...
Does it have to be in that order?
Gotta remember this cheat code.
 
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#5 ·
.boB said:
OK this is a strange one that I've never heard of. Coming back from the race track yesterday, towing my car trailer. The dash dings a few times, and "Check Trailer Wiring" shows up in the center of the dash. It easily resets, and immediately says, "trailer connected". This occurs every 5-10 minutes the rest of the drive.

This happens randomly and I can't relate it to speed, turn signal use, or road condition. it started while driving down the highway, not using the brakes.

I used to have a 2016 Colorado with the factory tow package. It developed the same problem, and became more and more frequent. Like every 2-4 minutes. Incredibly annoying. I "fixed" it by disconnecting the brake wire in the 7-way connector. Then I traded it in on my current 2020 Colorado Z71, and the problem disappeared. Until yesterday.

I had a trailer shop check over all the wiring, and all seems well.

Has anyone else had this problem? Is it a BCM? Or maybe the in-dash brake control module?
Click to expand...
If the trailer checks out, the next most common issue is the connector on the rear bumper. Check that there is no corrosion.

Next, check that the terminals are all still shaped properly. They should resemble an inverted V with the point facing out at you. One leg of the V is free and needs to have enough gap to make for a good tension fit in the trailer connector. Sometimes they can get smashed down and resemble more of a narrow U. You can get in there with a 90 degree pick and open them back up to the proper V shape.
Failing that, the receptacle is pretty easy to replace.
 
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#6 ·
Not sure, if order matters. I was told the main thing was that the CC needed to be turned off. Once I did that, I never had a problem towing or using CC while towing. I was told it was on same fuse as Brake controller or close.
 
Discussion starter · #8 ·
Well, it tried all of that - didn't help. there are no trouble codes, so no help there. I'm thinking of taking it to the dealer and see if it's something they've heard of, or can diagnose.

  • Same trailer, good wiring and lights. New plug.
  • started on my 2016 Z71 diesel at about 75K miles.
  • I traded that truck in for a new 2020, same configuration.
  • Problem disappeared, until the truck hit 75K'ish miles.
  • now it's back.

No codes. I cleaned the connections. I attached a load simulator for a couple of weeks - nothing. Connect the trailer - ding, ding, ding. Very annoying. But the trailer brakes seem to function fine.
 
#9 ·
Did you replace the truck side connector in the bumper? If so, are you confident the trailer side connector is properly seated/fully inserted into the truck side connector?

I replaced the truck side connector last year which resolved the corrosion issue I had causing the messages (with multiple trailers), but the aftermarket replacement I put in is a little tighter apparently and so I have to apply some force to ensure the trailer side connector is properly seated/fully inserted. One of the first trips I didn't realize that and obviously didn't have it secured enough, I was getting the warnings when hitting bumps.
 
Discussion starter · #10 ·
naskie18 said:
Did you replace the truck side connector in the bumper? If so, are you confident the trailer side connector is properly seated/fully inserted into the truck side connector?
Click to expand...
Yup, replaced the socket with an original Chevy part, and the plug with the best one I could find. Didn't change anything.
 
Discussion starter · #11 ·
Fixed it! I did a lot of searching on a few different Chevy related forums. No one has mentioned any problems like this from any Chevy truck that I could find. I also asked around the service dept at my local dealer. No one there had ever heard of this problem, either.

I searched through the Chevy parts catalog, and sure enough, I found a Trailer Brake Control Module. So I ordered it. GM 23337305 Trailer Brake Control Module Assembly
23337305 - GM Parts Giant

I installed it, and the problem appears to be resolved. I'm going on a longer trip in Aug, we'll see what happens.

The installation is very easy. The module is mounted on a vertical bracket, above the spare tire, next to the ABS brake control module. The job takes about 30 minutes to complete. I would post pictures, but Imgr isn't working again today.
 
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.boB
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