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 > New GMC 2500 Wont Engage Trailer Brakes

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Paroled

Illinois

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Posted: 12/10/21 04:18pm Link  |  Quote  |  Print  |  Notify Moderator

I have a new 2021 GMC 2500, Diesel. It will not engage trailer brakes unless the brake pedal is mashed to the floor. It is this way on any trailer it’s hooked up to. My 04 Silverado works fine on my trailer. Dealership could not diagnose. Opened case with GMC and they have sent engineers twice and no luck. Anyone hooked up an aftermarket brake controller to a new GM This has been going on for 7 months

ktmrfs

Portland, Oregon

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Posted: 12/10/21 04:40pm Link  |  Quote  |  Print  |  Notify Moderator

does the manual control activate the brakes? What is the setting on the brake controller?

On my 2015 Denali I have it set on 5 and activated brakes on both trailers, and I feel the trailer brakes when I check using the manual control slider.


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Paroled

Illinois

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Posted: 12/10/21 04:54pm Link  |  Quote  |  Print  |  Notify Moderator

It will work with the manual slide

kellem

Shenandoah valley,VA

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Posted: 12/10/21 05:30pm Link  |  Quote  |  Print  |  Notify Moderator

Wow,certainly frustrating and something I've yet to hear of.
Perhaps cheaper in the long run to install an aftermarket brake controller.

Have you invested in a brake tool to verify pad spacing. Possibly the trailer and not the truck.

riltri

Husk & Steinhatchee

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Posted: 12/10/21 05:39pm Link  |  Quote  |  Print  |  Notify Moderator

Find the fuses associated with the brake...I think there are 2. Take both out at the same time and reseat them. That will force the truck to reboot the brake controls. I have heard that has worked. Good Luck!!


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Thermoguy

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Posted: 12/11/21 09:20am Link  |  Quote  |  Print  |  Notify Moderator

If it works with the manual slide, then the brakes work and the controller. The issue seems to be the foot actuation dealing with applying the brakes on your truck. I wonder if that is controlled by a computer or by some actual physical connection. They might have to replace one of those items.

Lwiddis

Near Bishop, California

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Posted: 12/11/21 09:21am Link  |  Quote  |  Print  |  Notify Moderator

With a 2021 truck under warranty, demand Chevrolet fix it. Keep escalating up the chain of command.


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BenK

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Posted: 12/11/21 10:31am Link  |  Quote  |  Print  |  Notify Moderator

Too many potentials for these 'highly integrated trailer brake controllers', but IMHO, it sounds like the MC PSI sensor is the main culprit in your case

It might need bleeding and/or replacement



Edit...be careful, too often they just give up and replace subsystems/components/etc. trying to 'fix' it...

And, too often, the root cause is still there, but now masked by those new components/sub-systems...

Guessing this won't be just a GM thing, but all OEMs now have 'highly integrated trailer brake systems'...

* This post was edited 12/11/21 11:19am by BenK *


-Ben Picture of my rig
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LITEPHIL

AZ

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Posted: 12/11/21 11:15am Link  |  Quote  |  Print  |  Notify Moderator

So GM has sent engineers out and they can't figure it out but maybe someone here can? Doesn't it have a factory brake controller?


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ktmrfs

Portland, Oregon

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Posted: 12/11/21 02:31pm Link  |  Quote  |  Print  |  Notify Moderator

Thermoguy wrote:

If it works with the manual slide, then the brakes work and the controller. The issue seems to be the foot actuation dealing with applying the brakes on your truck. I wonder if that is controlled by a computer or by some actual physical connection. They might have to replace one of those items.


Since the manual slide works, that means the integrated controller knows a trailer with brakes is connected and it can power the brakes.

On my 2015, the integrated controller works so well that I don't feel the typical feedback one gets from a aftermarket controller as the trailer brakes get applied. Feedback is very subtle till you do a very hard stop. And I did have one occasion where I had to do a 60mph panic stop when a merging car decided to stop in the traffic lane! Control was amazing, ABS on the truck was full on and the trailer stayed straight as an arrow.

As you stop if your in tow haul mode does the dash indicator for the trailer brakes show the trailer brake force and does it vary as you change braking force? If so I suspect it is working.

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