14SLE

I have the same problem with the steering wheel controls on my '20 SLT and I'm glad someone else has confirmed it. The dealer, as usual, said they have never heard of this problem. At least 1-2 times on my 40 minute commute, I will press a "station advance" button on the steering wheel, the highlighted preset will advance on the radio, but the channel won't change properly. If you press the button again, it will change normally. Long-pressing the button seems to seek properly every time. In every regular (short) press of the button, there is a noticeable lag before the channel actually changes--probably because it's a networked connection instead of a direct analog connection between the radio and the steering wheel. I don't have an active Sirius subscription, so my presets are only FM/AM/FM-HD stations. I had a rental Terrain once with the same system (except non-NAV), and it did not seem to behave the same way--however, I didn't have it long enough to thoroughly test it. I will be going in for an oil change in the near future and I was planning to ask about it again. If you get a resolution, please post it here because my dealership will probably say "Never heard of this!"

Personally, I am not sure how you tell what system your engine has unless you have the original paperwork. Your 2014 would definitely have been AFM (8 cylinder/4 cylinder). I'm not positive, but I believe I read that 2019's with the 6-speed transmission still have AFM. I believe my salesman said you could order either AFM or DFM with the higher trim levels. My dealership only ordered DFM on trucks when it was available. The DFM is definitely a major improvement--I just hope it holds up over the long term. GM has had some bad engine experiments over time (350 diesel, Quad 4, 3.4L head gaskets, 3.6L timing chain, water-logged opti-spark systems, bad 305 camshafts, the list goes on...).

There are definitely times when I can tell DFM is active (rumble, vibration, etc.), particularly at low speeds. Fortunately, I have not started to hate it yet. The only options for full-sized trucks nowadays are: 1) Poor fuel economy (Toyota, Nissan), 2) Small engines with turbos (Ford), or 3) Messing around with variable displacement (GM, Ram). I have heard rumors that Toyota will be joining the turbo club on the upcoming Tundra (3.5L V6 with twin turbos). The use of adaptive ("learning") computer control can also cause issues because changing shift points and fuel delivery parameters can change resonant frequencies. As a software engineer, I honestly believe the "learning" capability is what ruined my 2014 GMC truck with AFM because the truck drove fine when I bought it. My drive to work has several long straight stretches where the speed limit is 35 mph and the truck began getting more and more aggressive at switching to V4 on those stretches even though it was lugging all the way. The dealership said it had "learned' my driving habits--I asked them to reset the system, but they couldn't (or wouldn't). I had to use the Range device or the truck was almost unbearable. There were certain RPM and speed combinations where the 2014 would vibrate loudly and those seemed to change over time. Using the Range device stopped the problems at the expense of fuel economy (around 2 mpg for me). Honestly, the AFM system wouldn't have been bad if it had only activated above about 45 mph. I could have set the minimum activation speed via tuning, but that risked my extended warranty. I am hoping the DFM system doesn't become as objectionable as the AFM system became. If it does, I will use the updated Range device until I decide what vehicle to get next. For those of you who are having vibration problems, the Range device is a good way to see if AFM/DFM is causing them without risking your warranty. If you plug in the device and your problems go away, it's probably the AFM/DFM system.

My GMC REV cover was installed by the dealership right after I bought the truck. I noticed a fair amount of water in the bed after a decent rain or hand-washing the truck. I realized the seals were riding a bit above the bed rail and adjusted the clamps to make sure the seals were actually sitting on the plastic rails. That was a five minute adjustment and it helped a lot. I still get a bit of water in the back, especially if I go through a car wash to get rid of road salt--mostly at the rear corners. This cover is definitely not as dry as the GMC cover on my 2014, but I really like the hard cover better than the pseudo-hard 2014 cover that was like a soft cover with hard inserts underneath.

I have a 2020 GMC Sierra crew cab SLT with the 5.3L (DFM) and 10-speed transmission. Having previously owned a 2014 Sierra SLE with the 5.3L (AFM) and a 6-speed, there is no way I would ever buy an AFM/6-speed combination again. You can tune out the driveability problems, but doing so will void your warranty. I know you can put the factory tune back on the truck, but there is a firmware counter that keeps track of how many times the truck's programming has been updated. My dealer recommended getting a tune whenever I complained about the jerky drive train, but they warned me to wait until the warranty expired. I did not make it to the end of the extended warranty before getting tired of it and trading it. I have put 13,000 miles on my 2020 in just a bit over a year. I drive 24 miles each way to work, mostly in the winter and on bad weather days (I have a "fun" summer car). My drive consists of country roads (35-55 mph) and a few small towns with stoplights. I routinely get 20-23 mpg on the display and spot checks show it to be pretty close. Like you mentioned, I use it to carry five people and general home improvement stuff. The truck works great for that purpose. Having had nine new GM vehicles in the family over the past 30 years, I will be totally amazed if my truck lasts 200k miles before I get tired of things breaking on it and get rid of it. I bought a long extended warranty, so GM will be fixing it for quite a while. Incidentally, I am a maintenance freak and the work is done by my dealer, so please don't bother telling me that I am doing something wrong with the maintenance...

I have not yet seen any consumer devices that tell what DFM mode is currently active. There is a YouTube video showing a GM engineer riding along with the reviewer--the engineer is holding a device that displays a fraction indicating the current DFM mode. DFM is much more complicated than simply shutting down individual cylinder(s)--it has 17 firing patterns it can cycle through (16 reduced cylinder patterns plus full V8 mode). There is a unique firing pattern for each mode where a cylinder fires a fraction of the number of times that it would normally fire for the specific number of engine rotations in V8 mode. There is a pretty good explanation of the system at this link, along with a graphical display of the fractional patterns. https://www.enginelabs.com/engine-tech/gm-escalates-cylinder-deactivation-with-dynamic-fuel-management/. GM claims it really doesn't make sense to say that you are only running on 'X' cylinders when that is not entirely accurate. The good news is, unlike AFM, the cycling of cylinders on and off should reduce concerns about uneven wear between the cylinders that are always on and those that shut down. Another reported AFM problem was higher oil consumption--I have not yet read anything that would suggest that DFM will be any better in this regard. I guess time will tell. I'm guessing GM prefers to NOT display the current DFM mode, because that would make it easier for the driver to blame a specific problem on DFM being active. Ignorance can be bliss (for GM).

My '20 Sierra SLT has the occasional shudder at low speeds--I particularly notice it in a school zone on the way to work. It appears to be a resonance that occurs at a specific RPM and/or speed combination with DFM active. However, giving it a bit of gas pedal clears it up quickly, so I have to say it is WAAAYYYYYY better than the old nightmare that was AFM (lurch, chug, lurch, chug). You can probably eliminate the shudder with a Range Technology AFM/DFM disabler if you cannot live with it and don't want to risk your warranty. I had a Range unit for my old truck that is on its way in for an update to the newest version right now. I will be curious to see how it works on the '20 truck and what effect it has on fuel economy. I probably won't use it much unless the DFM system gets more obnoxious over time.

I'm not really fond of the radio coming on when the truck starts, but the folks at my dealership say that's the way the radio works. It is annoying, but I would much rather deal with that than the more serious issues I have had in the past. I just turn my volume down all the way instead of turning it off. I hope there is an update to fix this issue, but I'm not holding my breath from past experience. So far, my 10-speed transmission has been flawless. I'm very happy about that, because I did not enjoy the 6-speed clank-o-matic in my 2014 and I didn't even make it through a test drive in a 2019 Denali with an 8-speed (the first 1-2 slam on startup did it for me). Good luck getting your issues fixed--hopefully, your dealership is helpful. Plus, enjoy knowing that your truck will probably get 1.5-2x the gas mileage of a Tundra. On my Toyota test drive, the DIC showed a trip economy of just under 12.5 mpg. I have talked to several Tundra owners who confirm that is about what they average. I'm hoping the upcoming '22 Tundra gets competitive fuel economy.

I previously had a 2014 crew cab Z71 with AFM and the 6-speed transmission. The combination of the "learning" transmission and the AFM system resulted in some horrible driveline clunks and jerks that never got better as the truck aged. I loved the looks of the 2014-18 models, but I was pretty much done with AFM-equipped engines and started looking at other trucks last fall. I liked the way the Titan drove (very nice and totally clunk free), but their resale value is awful. Tundras are nice, but ancient and get horrific fuel economy (yes, I know it is a truck and I can afford the gas, but I don't want a super-guzzler). Plus, Toyota's option packages are totally bizarre--the TRD sport package cannot be ordered on an upscale truck unless you get the TRD Pro, which does not even have automatic climate control. I test drove a '19 Denali at the end of the model year with an 8-speed, and the transmission slammed horribly before I even got out of the dealership lot. I passed on it despite a really good price. I test drove several 2020 models with the DFM system and 10-speed transmission and noticed no objectionable driveline behavior on any of them, so I traded my '14 on a '20 SLT/X31 when good deals were being made in January (pre-COVID). I have put about 13,000 miles on it so far, including a 1,100 mile interstate trip, and the truck still runs great. The DFM is aggressive and you can feel a "chuggle" at low speeds (20-30 mph), but nothing like the AFM system had. Unless the truck "learns" some bad behavior going forward, I'm pretty impressed with the DFM and 10-speed combination. I have averaged slightly over 20 mpg (per the DIC) for over 12,000 miles, including winter driving with remote start warm-ups. I drive about 40 miles round trip to work over back roads and drive a "fun" car during the summer. Manual spot checks of fuel economy suggest the DIC is reasonably accurate. The DFM system is rather complex, so we'll see how it holds up over time. I bought an extended warranty, so GM will be fixing it if it breaks. Overall, I have been quite happy with the truck so far. I have actually grown quite fond of the Multi-Pro tailgate and the seats don't make my back suffer on longer trips. I just wish they would stop making the trucks bigger each iteration--parking the new truck is like docking a yacht. My wife won't even consider driving it.

I had a 2014 GMC SLE Z71 crew cab pickup with the 5.3l (with AFM) and 6-speed. I had no problems with reliability, but there were a few annoyances with the overall drivetrain: 1) It seemed like the AFM became much more aggressive over time, even switching to 4-cylinder mode going up hills, etc. I ended up having to buy a Range Technologies box that I put on an OBD-II extension cable with a power switch to allow me to kill AFM during low speed limit stretches of road, otherwise it would continually switch between lugging (V4) and running smoothly (V8). 2) The 6-speed really didn't like to downshift unless you pretty much had it near the floor, then it would take off for the moon. There is a big hill near our house, and the truck would slow to a crawl going up the hill because it wouldn't downshift. I would keep pushing down on the gas pedal until it would finally shift. If the road were damp in any way, the rear end would break loose every time. My wife always thought I was being an @xx, but I wasn't trying. The transmission also went through a bad clunking phase for a while. I loved the looks of the '14, but I ended up trading it on a 2020 SLT with 5.3L (DFM) and 10-speed transmission. The difference is night-and-day. The 10-speed shifts smoothly and the DFM is definitely not as noticeable after 11k miles. However, I did put 67k miles on the 2014 with basically no trouble whatsoever other than a few squeaks and rattles. Hopefully, they have improved the drivetrain calibration since 2014, but you should (hopefully) be fine on reliability. Just keep up with the maintenance, especially the oil changes.