2021 GMC AT4 6.2L

[WhiteAT4]

Well boys-quite the plot twist here. Ive been informed that this is not the first but yet the third time in a span of only 12,000 miles and 12 months time that the motor has locked up on this specific truck.

The previous owner traded it in @ 38,000 miles after the second replacement motor locked up. The dealer fixed it and ive since purchased the vehicle and had the motor go out on me. You probably are wondering did I not look at the service record? I did-it is listed as “vehicle serviced-engine checked” nothing about being replaced. Long story short, I got screwed.

Motor lock ups @ 32k, 38k, 44k miles

Still trying to figure out the next steps so stay tuned.

 

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[Cohaagen]

What a nightmare. Sorry for you.

I am trading out of my 2020 6.2L before the warranty is up. As I have posted, mine has been fine (the motor at least). I don't recall reading about the problem on 2020s, but lots of 23/24. I'm likely gonna take the chance on the AT4X 2500 with gasser. I think that motor will be OK long term. The rest of the truck, with all the damn computers... I don't know. Scares me to own any of these out of warranty.

 

[elkchaser]

Just gotta ask, what fuel did you feed it. Manual says higher octane??? Regular won't cut it due to dieseling and what you are experiencing?

 

[WhiteAT4]

I do

What a nightmare. Sorry for you.

I am trading out of my 2020 6.2L before the warranty is up. As I have posted, mine has been fine (the motor at least). I don't recall reading about the problem on 2020s, but lots of 23/24. I'm likely gonna take the chance on the AT4X 2500 with gasser. I think that motor will be OK long term. The rest of the truck, with all the damn computers... I don't know. Scares me to own any of these out of warranty.

I dont blame you at all bud. That would probably be a good way to go.

 

[WhiteAT4]

Just gotta ask, what fuel did you feed it. Manual says higher octane??? Regular won't cut it due to dieseling and what you are experiencing?

No worries at all. Not everyone follows the recommendations-I have only put premium in the truck since I bought it because of the recommendation from the manufacturer.

This go around, a different dealership has installed the new engine and additionally the oil coolant system,hoses, radiator were replaced and they say that is a nationwide bulletin given out from GM that is supposed to fix the issue.

Just a warning for anyone in the market-beware of that carfax documentation. If it says “engine checked” ask questions and get repair work orders to see for yourself. I thought I bought a truck with all original parts.

 

[USMC(ret)]

Ahhh…

New member here & thought I’d chime in this thread for my 1st post since this happened to me as well. I joined the Silverado/Sierra Forum & posted about my experience here.

In that post, I talked about the 400a fuse that blew in the engine compartment (twice: replaced the 1st time, cranked & ran till it blew when the engine seized). If someone can confirm, I believe that 400a fuse is to interrupt the start cycle if the engine has issues turning over (ie: bearings beginning to seize). I learned after the dealership had swapped mine out that the 400a fuse had blown once before when the previous owner had it.

Like many, my confidence is shaken on this engine, but since this happened before my 1st payment, I believe I’m stuck with it unless I sell/trade for a loss. At least the warranty work was hassle free. Although it’s disheartening when the service manager basically says, “ahh another one…yup, we’ll get you another engine.”

 

[gemarsh]

Six.two.tic.tic.bang

Cannot believe there has been so many reported.

 

[USMC(ret)]

Six.two.tic.tic.bang

Cannot believe there has been so many reported.

Sadly, me either. Thanks for approving my posts (unless it was another mod - then thanks to them). Just here in MS, the dealer I took mine to said he had 4 ahead of me for this same issue this year. On the Silverado/Sierra forum, a member that’s a tech there said (& I called to confirm), there were 2 other dealers here in MS there was 2 in one lot & the other lot had “a few.” Nine including mine that I personally know of this year not including the 2(?) others reported in this post?

Makes me curious how many GM has replaced & what improvement they’ve done to prevent it from happening.

 

[Whaler27]

Me too, and even though all brands have their problems, these 24 GMs have me contemplating changing to the "F" brand... "the horror, THE HORROR!!"

My last GMC was a 1982 GMC diesel “Jimmy” - the Blazer/Tahoe of the day. The engine seized at less than 10,000 miles, and then it sat in the dealership for almost three months waiting for a replacement. When I got it back I was able to drive it for about 2500 miles before the transmission blew up. The failure rate on that transmission was so high they couldn’t make parts fast enough to keep up, so it sat in the shop for a couple months that time too. The third trip to the shop was an injector problem. After that it was another major transmission failure at less than 15,000 miles. This was all covered by warranty, of course, but in the first two years of ownership that vehicle was in the shop for almost eight months, and I wasn’t even towing with it. (That motor was gutless.)

COVID has gotten people used to stories like this, but in the 1980s parts and vehicles were available everywhere and dealerships had plenty of mechanics. It was unusual for a vehicle to remain at the dealership for two months or more…

When I got the Jimmy back after the last transmission fix I sold it as soon as I could. I took the worst vehicle financial beating of my life on that rig, because, by late 1984, everybody knew that 6.2 diesel was a complete piece of crap. I switched to a Ford pickup the following year and, until this new AT4X, I’ve been driving Fords, Jeeps, and Dodges for almost 40 years. That’s how long the taste of that awful GMC rig stuck in my mouth. I’ve never had another vehicle like it. I had little issues with the other brands, of course, but never anything that required more than a few days to fix, and never anything that stranded me.

I bought my 2500 because 1) the GMC ride was much better, 2) my job’s fleet experience with GM has been better than Ford over the last 10+ years, and 3) the Duramax/Allison combination has a great decades-long reputation for durability. Still, threads like this scare the heck out of me. I live and hunt in rural areas, often out of cell service and more than 50 miles from any town. Reliability is my number one concern.

 

[Cohaagen]

Ahhh…

New member here & thought I’d chime in this thread for my 1st post since this happened to me as well. I joined the Silverado/Sierra Forum & posted about my experience here.

In that post, I talked about the 400a fuse that blew in the engine compartment (twice: replaced the 1st time, cranked & ran till it blew when the engine seized). If someone can confirm, I believe that 400a fuse is to interrupt the start cycle if the engine has issues turning over (ie: bearings beginning to seize). I learned after the dealership had swapped mine out that the 400a fuse had blown once before when the previous owner had it.

Like many, my confidence is shaken on this engine, but since this happened before my 1st payment, I believe I’m stuck with it unless I sell/trade for a loss. At least the warranty work was hassle free. Although it’s disheartening when the service manager basically says, “ahh another one…yup, we’ll get you another engine.”

Can you clarify what year your truck is? I don't see it here and just skimmed your linked post. I think GM updated the dash on 1500 in 2023, so yours is earlier? You can also add this information to your signature so it is readily available.

 

[Cohaagen]

My last GMC was a 1982 GMC diesel “Jimmy” - the Blazer/Tahoe of the day. The engine seized at less than 10,000 miles, and then it sat in the dealership for almost three months waiting for a replacement. When I got it back I was able to drive it for about 2500 miles before the transmission blew up. The failure rate on that transmission was so high they couldn’t make parts fast enough to keep up, so it sat in the shop for a couple months that time too. The third trip to the shop was an injector problem. After that it was another major transmission failure at less than 15,000 miles. This was all covered by warranty, of course, but in the first two years of ownership that vehicle was in the shop for almost eight months, and I wasn’t even towing with it. (That motor was gutless.)

COVID has gotten people used to stories like this, but in the 1980s parts and vehicles were available everywhere and dealerships had plenty of mechanics. It was unusual for a vehicle to remain at the dealership for two months or more…

When I got the Jimmy back after the last transmission fix I sold it as soon as I could. I took the worst vehicle financial beating of my life on that rig, because, by late 1984, everybody knew that 6.2 diesel was a complete piece of crap. I switched to a Ford pickup the following year and, until this new AT4X, I’ve been driving Fords, Jeeps, and Dodges for almost 40 years. That’s how long the taste of that awful GMC rig stuck in my mouth. I’ve never had another vehicle like it. I had little issues with the other brands, of course, but never anything that required more than a few days to fix, and never anything that stranded me.

I bought my 2500 because 1) the GMC ride was much better, 2) my job’s fleet experience with GM has been better than Ford over the last 10+ years, and 3) the Duramax/Allison combination has a great decades-long reputation for durability. Still, threads like this scare the heck out of me. I live and hunt in rural areas, often out of cell service and more than 50 miles from any town. Reliability is my number one concern.

I do hope yours performs well and never leaves you stranded. Very true that an experience like yours can sour you for a very long time, or permanently.

My last 2 GM trucks have been solid. My 2015 Denali Duramax 2500 had the usual emissions problems - sensors going bad, DEF tank heater failure, etc. I also recall it had the water pump replaced under warranty at around 20k miles. My 2020 1/2 ton 6.2L AT4 was mostly perfect, aside from going completely dead one day, which I traced to the fuse box not being properly tightened down at the factory. It arrived with the pickup box almost 1/2" misaligned from the cab, but I never did anything with that. I would say it is one of the best vehicles I have ever owned, and a real jack-of-all-trades pickup. I don't think I have yet come across anyone with a 2020 having the 6.2L L87 fail. 2021 - 2024, many examples.

Still, I am completely done with cylinder deactivation and auto start/stop. Many new upper trim 1500s cost more than 2500s. Makes no sense. I'll take the HD with L8T.

 

[USMC(ret)]

Can you clarify what year your truck is? I don't see it here and just skimmed your linked post. I think GM updated the dash on 1500 in 2023, so yours is earlier? You can also add this information to your signature so it is readily available.

Will do - it’s a 2022