Kilgore Trout

Am I misreading your post? Did you say they have had since Monday and today "mentioned" lifters as a possible culprit? I mean, it should take a qualified tech about 20 mins to fully diagnose a collapsed DFM lifter.

A little late to the party, just saw this thread, sorry. The OP's mileage seems low to me. I own a 2021 Sierra 1500 AT4 6.2L with the optional Duratracs. I get about 13 around town (that is with almost zero highway miles). If I get even like a quarter of them highway miles, I can see over 16 on the averages pop up. If I stand on it stop sign to stop sign, I can definitely get sub 10 on the average, but that is driving like I am young enough to be worrying about acne.

Yeah, I actually can't say the decibels go up, maybe it is a frequency change thing. All I know is the bigger the blocks in the tread and the higher the load rating, the louder they seem to get as they wear. I too really like the tire (other than the noise). We go up on some pretty gnarly 4X tracks, this winter on some extremely icy and muddy trails and they seem to grip really well, better than I even hoped.

Pretty hard to attribute that issue to a failed DFM lifter. Given it wouldn't start after all the racket he described, I would suspect it was something a little more dramatic.

My AT4 came with Duratracs. I like the tire off road and seems to be doing well on the ice/snow we have had so far. They are freaking loud and as new as they are now, I know they will be REALLY loud at 20K miles. I am too cheap to replace them until they are worn out but definitely am not looking forward to the deafening din to come.

If Idle Hours are not included in Total Hours, somebody at GM is functionally illiterate.

My Sierra 6.2L 1/2 Ton AT4 is my third vehicle (least used). It has sat for a couple of weeks a couple of times since I bought it. It is pretty cold here as well, never failed to start. I would seek out a new dealer for maintenance.

I was referring to a link of a report of DFM lifter failures on the "non-DFM" engines.

I used a fish tape I had laying around and sent it up from the bottom the route I wanted it to follow, taped the cable run I wanted to pull back down to the end of the tape and pulled it through. You can buy them for under $10, it doesn't need to be super long.

I had intended to buy a Backflip MX, but found something a little less expensive and given its many good reviews, thought I would give it a shot. It took about 30 minutes to install and it keeps the weather out just fine, but clearly is not as nice looking as the BF MX. I have used my bed quite a bit since installing the Gator SFX and it is super simple to fold it up and roll it back out when I am done with hauling whatever. https://realtruck.com/p/gator-sfx-tri-fold-tonneau-cover/v/gmc/sierra-1500/2021/

Personally, if my dealer couldn't diagnose it, I would find another shop. Parasitic drain can be challenging to nail down, but a competent shop will find it.

Got a link to such a report? I have not seen any.

GM built some 21's without DFM (turned on), it was reportedly due to the chip shortage. Your Monroney window sticker calls it out.

Certainly couldn't hurt to take it to a trusted shop and have them check the alignment.

Totally agree.

Sounds like they eliminated the transmission as a possible source of the noise. If you have another dealership within reasonable driving distance (could be a Chevy dealer just as well), maybe take it to them and tell them what has been done so far, maybe they have someone on staff that has seen a similar problem before. If they get it right away, maybe consider switching dealers for work going forward.

You can buy a cheap (like $20) scanner that plugs into your ODB II port and will connect to a smart phone and a free app, that will read engine codes. If the condition that turned on your CEL set a code, it likely will be there.

Hope you can get it working OP. I have one on my '21 AT4 and absolutely love it. I actually don't use it to climb into the bed as I have found the helper bar and the side steps work better for me, but I use the multifunction gate fully folded down as a bench when putting my hiking boots and snow shoes on. Just this morning we had a hike on one of our favorite trails that was very icy and snowy. We had our micro-spikes on our boots, so just put them in the bed until we got to the trail head. Super easy putting our boots on, sitting on the lower step fold out section, real easy to reach the laces.

They look like the optional 275/65-18 size in maybe K02's?

That deer definitely didn't make it. Glad you are OK, sheet metal and plastic can be fixed. Deer don't get oncoming head lights. I fed two orphan fawns all summer as their mom was hit right out on the road that runs beside our house. I had watched them with their mom a few days over a few weeks before she was hit. The mom was hit when they were really young (large dog tall at the shoulders). I was pretty sure they wouldn't make it. I knew they were partially weaned when they started eating the Antler Max but thought at their age without a mom to show them the ropes, no chance. Most of the fall they were nowhere to be seen and I thought for sure a predator picked them off (or another car, maybe up the road a ways). About a week ago, I saw them both out back, looking for the Antler Max. My wife said, "you better go get some of that deer feed and load the tub up, they are back..." Deer breed like rabbits.

I have a 2021 Sierra 1500 AT4 6.2L. Merceds Benz tight and quiet. I would ask my dealer to take a look at it, mine doesn't have any creaks, clunks, pops, nada.

There is a device you can install that allows you to control some of the tuning parameters including DFM (thus, turn it off), it is called the Pulsar LT. The DFM lifter problem is contained to early 2021 MY trucks which had a bad batch of lifters installed (built before 3/5/2021). I have a 2007 Yukon I bought new that was the first of the AFM engines. It uses the same exact lifter design on my AFM system as the current DFM lifters. When I first started reading Internet forums on these trucks, the "problem" with AFM lifters was a major topic. I became quite concerned that my 2007 "long in the tooth" AFM lifters in my Yukon were going to fail. I asked my dealer service advisor, the same guy I have been using since I started going to that dealer and a VERY experienced guy on these trucks, if we should replace the AFM lifters in my truck as a preventative measure. He said, "I have read about these AFM lifter failures, but we have never seen one in person (this is at a GMC dealer who is largest in the area in sales and service). He said, "just keep maintaining your truck like you do and quit worrying about your AFM lifters". Recently, he (like every GM dealer who sold these early MY 21 trucks), have now "seen" DFM lifter failures. He had kind of a worst case scenario in that one of his fleet customers bought a batch of early 21 MY trucks and had multiple trucks go down with failed lifters. Early on, they just replaced the bad lifter. Then they realized some of the trucks were coming back with another failure, so they started replacing all 8 on the bank that had a failed lifter. Then finally they realized if you have a failure of one of the lifters, you have a higher probability that another one will fail (of the originals installed when the engine was built) and it can just as easily be in the other bank as the original failure side, so now they replace all 16 lifters anytime they have the first one fail on any engine built in the bad lifter date range. Personally, I am basically in the same boat as you in that I own a 2021 Sierra 1500 6.2L that was built later than the bad lifter cutoff date. I considered the Pulsar LT, but have made peace with the notion that as long as I maintain my new Sierra, like I have my 2007 Yukon, I have about the same likelihood of a lifter failure as I have for the last 15 years of owning my Yukon. I can live with that, so I quit worrying about DFM lifters.

I definitely do. I bought one of those clone Tech 2 scan tools for my 2007 Yukon. I would set it up and watch the knock sensor and timing ****** functions on my 5.3L (LMG) engine while driving around town and short highway jaunts. This engine has a compression ratio of 9.9:1. Even around town the knock sensors were constantly lighting up with a corresponding timing adjustment. What I determined is the tuning of the ECU has the engine "ride the knock sensors" for final timing adjustment. There were times when I noted the timing was actually retarded to ATDC... While I suspect the 6.2L engines (with their higher compression ratios) can run "safely" on regular gas, due to the sensitivity of the ECU and its sensors, you are going to sacrifice performance with lower octane fuels and I think are depending everything in the sensor loop to be working really optimally to avoid damage. Where I live 91 is the highest octane I can buy from a pump. The cost is always about +10% or less for 91 over 87. When I do the math, in the big picture, it just isn't enough to worry about so I follow what the owners manual recommends.

All I know is my new 6.2L AT4 Sierra is a lot more spirited than my 5.3L Yukon. It would have to be a few car lengths at least in the 1/4 mile. It is also a few MPG less around town and that is me with an egg taped to the bottom of my foot when driving the truck.

I suspect this is a little more than you were looking for, but I saw it on a post on these threads and felt it was one of the best I have ever seen. https://chassisunlimited.com/2019-2021-gmc-sierra-1500-octane-front-winch-bumper.html