Automatic Transmission Control Module Problems of GMC Sierra 3500

My truck has been exhibiting hard downshifting at certain speeds, when the powertrain loads up such as a grade change, and requires a downshift. I have complained about this issue to the dealership as early as 2022, and 33,185 miles. The dealership made me pay for a transmission $388. 90 flush which did not resolve the issue. The problem has become progressively worse, to the point where the toll road transponder fell of my windshield during a recent harsh downshifting incident. At the same time there was an existing mil and derating for a def heater and nox sensor failure, so during a warranty visit I asked that this transmission issue be addressed. On Friday March 13, the dealership called and said they confirmed the hard downshifting, albeit not as extreme as I described. The technician said that the valvebody needs to be replaced. At the same time, they performed a tcm flash for the 10l1000 momentary wheel lockup recall. The dealership then said they could not get the truck to set a p0747 code, said that gm refuses to replace the faulty valve body, and recommended I take the vehicle home unrepaired, and to come back when the p0747 code is set. I requested they continue to drive the vehicle. Today March 20 the dealership called and said they could not get the code to set, and that I need to drive the truck and come back when the code appears, despite the truck exhibiting clear symptoms of a progressively wearing feed limit low valve. N242454441 does not seem to indicate a p0747 code is required to replace the valve body. This vehicle is not safe for towing a 20,000+lbs and GMC is refusing to repair a transmission with symptoms congruent with n242454441. The dealership still has possession of the vehicle and wants $360+ in diagnostic labor.

See all problems of the 2020 GMC Sierra 3500 🔎.

My 2011 fmc Sierra 3500 drw denali suffered a failure of the transmission control module (tcm). I could barely move the vehicle and almost got into an accident merging into traffic. Forward and reverse was affected. The transmission reverts to top gear after the failure, and makes driving very difficult. There was no warning for this failure luckily I was minutes from my dealership. This problem could be bad.

See all problems of the 2011 GMC Sierra 3500 🔎.

Gm transmission control module # 24256861. . . . There are over 9,000 gm trucks that are sitting idle because gm quit making this part, there are no after market replacements nationwide. When this part fails it shifts the transmission into 2-3 rd gear and goes into limp mode which if you are doing 70 on the interstate you are in for a sudden awakening. It also causes other issues like stablitrac issues there are at least 4 other issues which make the vehicle undrivable it is sad that gm has known of this failure for well over year. It should be a warranty item but is not. I just need my truck to be drivable again. . . . .

See all problems of the 2013 GMC Sierra 3500 🔎.

Apparently a common issue. The tcm (transmission control module) failed and the vehicle will not start or shift. Vehicle went into limp mode on highway while towing a trailer. Part availability unknown and on backorder for a year.

Transmission control module tcm failed while driving down the freeway i84 in boise idaho. Ac delco part number 24256861. This caused the truck to go into limp mode when at highway speed. While in limp mode the truck would not respond to throttle commands. Truck slowed to 20mph causing a disruption in traffic flow and making it very difficult to get off the freeway, dodging traffic. The tcm failure has been confirmed through a local GMC dealer (dennis dillon in boise idaho). The manufacture (general motors) has discontinued manufacturing this part leaving my vehicle and thousands of others failed. Gm's responce is the part is on a national backorder. 24-26 months at the earliest. Aftermarket support is none existent. There were no warning lamps or messages or symptoms prior to the failure. Very limited parts are available on ebay (10 or less) . Dealer price for the tcm is $710. Ebay pricing is 4-10 thousand. Gm customer assistance provides no answers and fails to ackowledge the safety concern of the failed transmission controller.

See all problems of the 2014 GMC Sierra 3500 🔎.

I drove my wife to the pharmacy and after pulling out of the parking lot onto palmdale road in victorville the truck went into to limp mode. The transmission locked up into park at 25mph almost causing a rear collision behind us. The GMC Sierra 3500hd 2009 came to a screeching stop causing a bit of whiplash to my wife and daughter on board. The tcm transmission control module along with the allison transmission failed causing this close accident. The vehicle is inoperable at this time. This is a dangerous defect.

See all problems of the 2009 GMC Sierra 3500 🔎.