usmcav8or

What are the exact windows for the valve springs and lifters, and how did you check to see if your truck fell in those windows?

I would give the GM truck a little while, see how it goes, mine hasn't given me a lick of trouble ever since they re-did the crankshaft re-learn procedure, maybe that will be the case with yours as well? I think Toyotas are great, but I also really don't like buying the first year (or two) of any new model vehicle, seems like they always have some issues that require design modifications. I'm hoping to own this truck for 4-5 years, put 100k on it, by that time the Tundras will be a known quantity and there will be other new stuff on the market to choose from. I personally love turbos, you get a huge increase in power for a small risk of having to eventually replace the turbo, which isn't even a big deal nowadays as the turbos are becoming super reliable, so although I really like the power delivery of this 5.3L, my guess is my next truck will be forced induction, I really don't see NA engines hanging around that much longer anyway, seems like every manufacturer will soon be forced induction as the mainstay offering. I really love this AT4, as long as I don't have any more issues, I'll enjoy it for a few years.

There are several good ceramic companies out there, like I mentioned, I've had really good results with CarPro UK formula, it's about $60 for a bottle that will do one car with some material left over (I've done 2 small cars with the $60 bottle). Here is a video comparing a bunch of them, you can see the CarPro UK performs great: CarPro also makes a really cool product called "CQuartz", it's designed to seal your wheels, but you can put it on grills, etc., and that stuff is freaking amazing. When I had sports cars that generated a ton of brake dust the CQuartz was like teflon, kept the wheels looking factory new for years.

El Camino, You couldn't be more wrong about that, maybe actually try a product before you pass judgement, there are several good YouTube videos testing ceramic coatings in real world weather, and clearly, it isn't snake oil. I will say that there are plenty of cheesy products claiming to be "ceramic technology" that are just marketing hyperbole, but a legit ceramic coating is far superior to any other type of wax or sealant, I have cars that are 3+ years old that still bead like they were waxed yesterday. Ironically, you're chastising ceramics and then in the same breath recommending Ziebart? Seriously, is there a more cliche example of a snake oil company out there LoL! Like what do you think they're giving you for $99? Maybe Google "truth of dealer paint protection" and realize how bad you're getting ripped off, because Ziebart is probably the exact same over priced garbage the dealership sells people.

I'll second the recommendation for ceramic coating, I apply it myself to all my vehicles (I used to be into sports cars), it's a fair amount of labor, but worth it in the long run because it's the ONLY product I've found to have true staying power on the paint, even the expensive polymer sealants don't last much more than 6 months, whereas ceramic lasts 2-5 years depending on environment. I use CarPro UK formula, works awesome. You can pay a detail shop (going rate is $800+) but you're paying for their time, it's maybe $30 worth of material.

Update on mine: Put about 3,000 miles on it since the second dealer visit, I called them to let them know they can close the ticket and service advisor said "I guess the second re-learn procedure did the trick", so my only advice if you have the nuisance CEL light is to make sure the mechanic does the crankshaft re-learn procedure correctly (and don't be surprised if they have to do it twice), in any case mine is now fixed. I actually really, really like the 5.3 motor, I'm getting 20 mpg in mixed driving and it has plenty of grunt when I need it, I think it's the right balance of power and mpg in a 1/2 ton for most people. The 10 speed tranny is great, trucks rides great, comfortable cabin, so I'm happy with it (for now LoL).

It's been a little over a week since I got mine back from the dealer and still no SEL light, but I haven't driven it very much. I'm hoping what may have happened is that when the tech updated the ecu software and did the crank relearn procedure on the first visit, that perhaps the relearn procedure was not done correctly or didn't take, I know those kinds of procedures can be glitchy and the instructions for doing them are often confusing. When I took the truck back the second time he kept it in the bay for about 45 minutes, my guess is he did the crank relearn again, (at least that's what I'm hoping), time will tell. I'll give premium a shot and see if I notice any difference, but I have to say that may be just you getting used to the truck. Speaking for myself, (now that I have 2500+ miles) mine seems to be running smoother overall as well, I don't know if that's the tranny smoothing out as it breaks-in and learns driver behavior, or if it's just me getting accustomed to the feel of the vehicle, I also noticed that after the software update it seemed to run smoother overall. I'm skeptical that premium would make a big difference in a NA V-8 motor, by design they just shouldn't be very sensitive to that kind of thing (as opposed to forced induction engines), not to mention the fact that where I live premium is about $1 more per gallon, and that's totally not acceptable to me to pay that as a huge fuel surcharge over the lifetime of the truck, it needs to be able to run on regular grade fuel.

mine was made in Silao plant, Guanajuato, MX, 06/2021

I completely understand what you are describing, ditto here as well, it's just that I have no experience with any other GM product, so I don't know if it's the tranny hunting, or if the motor is just a little loaded down at low rpm so the manner which it lumbers along is kind of normal? I also suspect I'm "feeling" the DFM system doing it's thing, which in my opinion would make the engine run a smidge rough as the cylinders are cycled off, so perhaps that's just "normal" DFM operation as opposed to misfires. It seems to run a little smoother in L9 (which purportedly shuts off DFM, but it's subtle, so hard to say for sure). It further proves what a dumb decision GM made in going down the AFM/DFM road, I would rather they have gone the Ford road (forced induction), you get way more efficiency and power out of it, and modern turbos are pretty darn reliable (especially relative to this stupid DFM system). What really should be happening is that GM engineering should be seeing these forums and respond!

I took mine to dealer this a.m., mechanic pulled code P0300 (again), couldn't find anything else wrong, he asked me to drive and monitor for a couple weeks and he'll keep the service ticket open. I'm willing to let the dealer give this an honest try, but bottom line is they don't know what's wrong with it, let alone how to fix it, and really it's a design flaw from the factory. It's very concerning how many 5.3's have had this problem, I found a similar thread on another site, seems there are a slew of Trail Boss owners reporting same situation. Lemon Law's vary by state, I've already looked at how it works in mine (MD), I would like to believe that this issue can be resolved because I really do love the truck otherwise, it rides great, quiet cabin, nice radio, the 5.3 is actually a really nice motor, the 10 speed tranny does a great job, literally have nothing but praise for the truck, but obviously this situation with the SEL is absolutely 100% unacceptable. It totally baffles me what thought process led GM to conclude that the AFM/DFM was worth the hit to reliability and their brand reputation, the customer aggravation, etc. All that to get a fleet increase of 1 mpg?! Tundra's get 14-15 mpg and people love them because they are a bulletproof rock-solid reliable powerplant. What customer would chose 1 mpg if it meant introducing the complexity of DFM, nobody would be dumb enough to do that (except a GM engineer). I will certainly report back with updates, hope others will post their experiences as well. It would be interesting to know manufacturing dates of the troublesome trucks?

So, full history so far on brand new 5.3L Sierra AT4: SEL at 900 miles, cleared code myself (P0300), SEL again at 1600 miles, took to dealer, they did service bulletin 21-NA-154, (update ECU and relearn on camshaft sensor), driving home tonight at 2200 miles, SEL is on again. Plan to contact dealer tomorrow, very upset, if this isn't fixed asap, I'll have to start looking into remedy under lemon laws Info from anybody else having this (or had this) as an ongoing issue is appreciated.

To the OP, kmeleon, you are describing EXACTLY the behavior of my brand new 2021 1500 AT4 w/5.3, mine did the CEL light at 937 miles, and again today at 1300 miles, the first time it happened I pulled and cleared the P0300 code myself using a scanner, today it cleared itself when I shut the truck off and restarted it. This is my very first GM product and like you I also love everything about the truck, but holy cow what a POS system this DFM is, I don't have time in my life to go to the dealer so he can chase random P0300 codes, I am so pissed and disappointed in this truck, don't know why I gave GM a shot, my concerns about their poor quality were spot on, and now it's biting me, I wish I would have waited for the new Tundra Any updates you have on your case are appreciated, I intend to take mine to the dealer asap, although reading the forums it seems like I'll be wasting my time having them try to chase down a spurious code....

I have a week old 1500 AT4, just threw the P0300 code with 967 miles on the truck, this is my very first GM product, holy crap, why can't American companies build a reliable product?!! I don't want to drive a Japanese truck, but damn it, American cars are so freaking awful I don't have time in my life to take cars to dealers, if this keeps happening, it's back to Toyota (where I NEVER had a single freaking issue with two of them in over 250,000 miles combined!)