GMC Sierra 1500 Faulty Trailer Brake Controller

Class Action Investigation

By Brian Jones | Updated on

By Brian Jones | Updated on

Lemberg Law is investigating complaints that the 2022 and 2023 GMC Sierra 1500 have a major problem with faulty trailer brake controllers. Vehicle owners with integrated trailer brakes report that when they try to pull a trailer, they get malfunction messages, and then their trailer brakes are disabled.

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Is There a Problem with the Trailer Brake Controller in the GMC Sierra 1500?

There is a serious fault with the trailer brake controller in both the 2022 and 2023 GMC Sierra 1500s. When drivers hitch up their trailers and attempt to drive, they get error messages. These are followed instantly by a message that their trailer brakes have been disabled. Their trailers don’t have brakes once they start to tow!

Consumers have been complaining to the National Highway Traffic Safety Administration (NHTSA) about the problem. There are also ongoing discussions in the GM Trucks forum that describe the issues owners are experiencing.

General Motors Company (GM or GMC) knows about the problem and has told dealerships over and over again that their engineers are “working on a fix.” But that’s about as much as they have said publicly.

Some forum members have had conversations with GM representatives and have shared their feedback in the group. The forum is for Chevrolet Silverado and GMC Sierra trucks, both of which are manufactured by GM. And, as it turns out, both the Sierra and Silverado have the same trailer brake fault.

On October 19, the owner of a 2022 Silverado Crew Cab LTZ posted that he’d received an update from his dealer stating that there was “a fix in process. GM engineers have redesigned the controller and now we are waiting for the redesigned controller. They are estimating about a month before the replacement part will be available.”

On November 7, the member who started the faulty trailer brake controller thread posted an update. The owner of a 2022 Chevrolet Silverado LT Trail Boss, said he’d been told GM’s brand quality team was working on a fix they hoped to roll out between Thanksgiving and Christmas 2022.

GMC Sierra Trailer Brake Controller Service Bulletins

GM has published several bulletins about the malfunctioning integrated trailer brake control system. They now confirm that it affects multiple truck models manufactured by GM including the 2022 and 2023 GMC Sierra 1500.

While it is required by law for vehicle manufacturers to provide the NHTSA with copies of all manufacturer communications with dealerships, only two of the bulletins are available on the NHTSA 2022 GM Sierra page. They were posted there on July 22, 2021, and Sept 27, 2022.

The first, PIT5509H, provides preliminary information on how to “diagnose and repair” vehicles that display Check Trailer Wiring or Service Trailer Brake System. Clearly, the repair didn’t work.

The second bulletin also contains “preliminary information.” It states that when consumers “connect a trailer to the truck that there is a Service Trailer Brake message displayed in the DIC. When checking for DTCs a C159C sym49 may be set for the Trailer Brake Control Switch. GM Engineering is aware of the issue and working on a fix.”

By the end of November 2022, there were no updates on file with the NHTSA for the Sierra 1500 trailer brake fix.

Other Bulletins

These are bulletins that aren’t currently on the NHTSA website.

A service bulletin, 21-NA-155, published earlier, in June 2022, also states that customers were complaining about Check Trailer Wiring and Service Trailer Brake messages displayed on the Driver Information Center (DIC).

But it tells dealerships the cause of the problem might be a poor connection at the 7-way trailer connector at the trailer and/or the vehicle side. It also mentions poor-quality aftermarket trailer plugs, many of which don’t comply with the SAE standard specifications.

The most recent bulletin, PIT5948A, is dated October 6, 2022. It updates the condition, but not the cause. It reiterates that the Service Trailer Brake message displays and says, “When checking for DTCs, a C159C sym49 may be set for the Trailer Brake Control Switch. This condition could be intermittent, and when the fault is present the electric trailer brake functions will not be operational for that key cycle.”

This bulletin says, yet again, that they are “working on a fix.”

What Problems are Sierra Owners Experiencing with the Trailer Brake System?

When GMC Sierra 1500 owners hitch a trailer of any sort to their trucks they get malfunction messages and, generally, their trailer brakes are disabled. What this means is that they are unable to tow a trailer with the Sierra. And, the horrible reality is that most owners have bought their Sierra as a towing vehicle, often for RVs and boats.

Fortunately, there haven’t been any accidents due to the faulty trailer brake system yet, but there have been some close calls. For example, a 2022 GM Sierra 1500 owner from Texas states in a complaint to the NHTSA that in March 2022, he “almost had an accident because of the brake system failure.”

Complaints to the NHTSA

An owner from South Carolina states that he had owned his Sierra for 4. “ I went to trailer our new boat and trailer with EOH (electric over hydraulic) braking system.” But on the ride home, he got the trailer brakes disabled message “and lost all braking to the trailer.”

After doing some research, he “found out that many others with GMC Sierras and Chevy Silverados had had this issue now for the past 3-4 months with GM still not having a solution yet. We all have defective and very dangerous vehicles losing all braking with the trailer due to this issue. They need to be pressured to get this fix ASAP before someone dies.”

Having purchased a new Sierra on October 17, 2022, an owner from Virginia tried to tow a 7,300 lb travel trailer 4 days later. When he started towing the message Trailer Brake Disengaged Service Required illuminated. He states that the ”trailer is (a) 2023 Airstream with no brake failure,” complaining that “Disabled trailer brakes (are) not safe to operate. GMC Dealer acknowledged the failure but (they are) unable to fix.”

An owner from New Mexico has had a slightly different experience. He gets error messages, but it doesn’t always happen immediately. “When I connect my trailer that has trailer brakes, the system recognizes my trailer and the trailer brakes work until I try to drive. I get an error message Trailer Brakes Disabled Service Trailer Brake System. This may happen within a few feet or the longest is about a mile. GMC has no fix and the dealer, while cooperative, didn’t/couldn’t troubleshoot the problem as the above PIT has no known corrective action.

“Now I own a truck that has the ‘Max Trailer Package’ that is rated to pull 13000 lbs but has no trailer brakes.”

Discussions on the GM Trucks Forum

Discussions about faulty trailer brake controllers on the forum involve both Sierra and Silverado.

Responding to comments by Silverado owners, a new forum member says: “Well I am glad I saw this post. I just picked up my new boat in my 3-week-old Sierra 1500 2022.5. The trailer has the EOH braking and on my way home I kept getting this message, then it would go away then come back. Finally, 2 miles from my house this disabled message came on, and no more trailer brakes. I thought it was a trailer EOH fault, but clearly, it’s my truck. I wish we would know when this fix is coming. I can’t trailer a 9.5k boat/trailer with no trailer brakes.”

The owner of a 2022 Sierra 1500 Elevation had a similar experience. “Got the truck 2 weeks ago and last weekend took the camper out for the first time with the new truck. The brakes worked (for) a short while, (but) then I got the same message and the trailer brakes wouldn’t work at all. I pulled over, shut the truck off, disconnected the harness, and plugged it back in. Same thing. It worked for a short time, then the error message and total loss of trailer brakes.

“After the third time of this nonsense, I gave up. When I got home, I checked my wiring on the trailer and all was good. I know I didn’t have a problem with the trailer brakes with my old truck and towed my trailer the week before I traded it in. This condition is highly dangerous.” About a week later, on November 8, the dealer told him it was a brake controller error. “They said, GM doesn’t have a fix yet.”

What Should You Do if Your Sierra 1500 has Trailer Brake Problems?

Lemberg Law is investigating complaints about the Sierra 1500’s faulty trailer brake system. If you have experienced problems, we’d like to hear about them. You might qualify for our class action investigation.

If you’d like to join the investigation, please call us at 844-928-4443 or complete our case evaluation form. We will evaluate your case and see if you qualify. It won’t cost you a cent because the law says that GM must pay all legal bills for lemon law cases.

Brian Jones

About the Author:

Brian Jones spent more than 20 years working as an ASE Certified Master Tech and Parts Specialist at multiple dealerships. Brian has become an authority in the industry, traveling across the country to consult for car dealerships and contributing his expertise as a writer for several major automotive publications. In his spare time, Brian enjoys working on pickup trucks, muscle cars, Jeeps and anything related to motorsports.

See more posts from Brian Jones
  • DK

    Carbon copy with “M G” above. Need to tow a 7K lb. trailer (loaded) and can’t do so without brakes. Only reason I bought truck (Elevation purchased November ’22).

  • John J

    I also have a 2022 GMC Sierra 1500 SLT equipped with the 3.0 diesel and the max towing package. I purchased the truck new at the beginning of August 2022 from Alpine Buick GMC in Littleton, CO. I have not been able to use my travel trailer due to the same trailer brake issue. While waiting for and expecting a fix for trailer brake issue I have also purchased a $4100 Leer topper and $700 bed rug. Now I am faced with the hardship of losing out on a lot of money and choosing another truck or selling my camper because I can’t tow it.

  • Dennis H

    This is not a new problem going back to 2008 or more. Many online have expressed problems and no fix seems to work. Please dig deeper into this problem. Thanks

  • M G

    Great write up. I have the same issue pretty much word for word as written here on a GMC Elevation l which is 3 weeks old. Purchased mid November 22.

    Purchased a brand new trailer and can’t use it.

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