Squeaky belt or pulley on 6.2 HC

Stans2019AT4 · May 15, 2020

I have a 2019 GMC AT4 6.2 with a noise at start-up that sounds like a bearing in one of the pulleys or belt tensioner is bad. I noticed it around the 3,000 mile mark. It is worse during cold starts and it is almost a squealing noise. I took it in to the dealership who had it for almost a week, and finally determined the noise was coming from the catalytic converters and there was nothing they could do about it. They even put the truck up on the lift and had me come in to listen to see if it was the same noise I was talking about. And yes the noise was actually coming from the catalytic converters. I guess this is normal but it really sucks! My 2017 Chevy Silverado that I traded in for the AT4 did not make any noise, just saying! Stan S.

Jav_eee · May 16, 2020

I have a 2019 GMC AT4 6.2 with a noise at start-up that sounds like a bearing in one of the pulleys or belt tensioner is bad. I noticed it around the 3,000 mile mark. It is worse during cold starts and it is almost a squealing noise. I took it in to the dealership who had it for almost a week, and finally determined the noise was coming from the catalytic converters and there was nothing they could do about it. They even put the truck up on the lift and had me come in to listen to see if it was the same noise I was talking about. And yes the noise was actually coming from the catalytic converters. I guess this is normal but it really sucks! My 2017 Chevy Silverado that I traded in for the AT4 did not make any noise, just saying! Stan S.

Because it’s normal on a 6.2. Watch any exhaust video on YouTube you want. You’ll hear it. Nature of the beast.

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Eljeffe316 · May 16, 2020

Mine also started right at the 3000 mile mark... prior to that it sounded perfect! Seems like quite a few mention it around this approx. mileage.... GM needs to find a solution for it. Hope someone figures this out...

FishHuntRepeat · May 18, 2020

Well crap....if it is the Cats now what? how to fix? For the record mine has done it since day one so the mileage didn't play into mine. I would like to start mine with the belt off but I am afraid of what codes or check engine lights will come on or be stored, has anyone tried this yet?

AT-FORE · May 26, 2020

I just purchased a 2020 AT4 with the 6.2, 10 speed. I have about 720 miles on it and have already had it at the dealership for the exact same squeaking noise. My dealership told me they could not replicate it and the noise is either the high pressure fuel pump or dry sump oil pump. I know neither one of them are the culprit because the truck does it on startup and constantly between 1000-1600 rpm when driving. Its not the fuel pump and its not the oil pump. It sounds like a bearing and it is extremely annoying. I drive a lot in the mountains on slow winding roads and the noise is extremely loud in this type of environment. I also thought about putting exhaust on it thinking it would take care of the squeak, but I'm glad I read through this forum before I spent the money. It sounds like this squeaking noise is "normal" but does there is still no true answer. Its quite embarrassing when I spend this kind of money on a truck and the first thing my wife says is "It squeaks, whats that noise", I sound real dumb when I tell her "Oh, they say its normal, don't worry". I went from an 07 Tundra to this and there is no comparison, the AT4 is amazing, but this squeak is absolutely obnoxious. I have never owned a GM vehicle but at this point, I hope I made the right decision.

I will take it to the dealer once more and have them ride along for them to hear. I will also contact the GM social media posted in this forum.

SilentSierra · May 27, 2020

14 hours ago, AT-FORE said:

I just purchased a 2020 AT4 with the 6.2, 10 speed. I have about 720 miles on it and have already had it at the dealership for the exact same squeaking noise. My dealership told me they could not replicate it and the noise is either the high pressure fuel pump or dry sump oil pump. I know neither one of them are the culprit because the truck does it on startup and constantly between 1000-1600 rpm when driving. Its not the fuel pump and its not the oil pump. It sounds like a bearing and it is extremely annoying. I drive a lot in the mountains on slow winding roads and the noise is extremely loud in this type of environment. I also thought about putting exhaust on it thinking it would take care of the squeak, but I'm glad I read through this forum before I spent the money. It sounds like this squeaking noise is "normal" but does there is still no true answer. Its quite embarrassing when I spend this kind of money on a truck and the first thing my wife says is "It squeaks, whats that noise", I sound real dumb when I tell her "Oh, they say its normal, don't worry". I went from an 07 Tundra to this and there is no comparison, the AT4 is amazing, but this squeak is absolutely obnoxious. I have never owned a GM vehicle but at this point, I hope I made the right decision.

I will take it to the dealer once more and have them ride along for them to hear. I will also contact the GM social media posted in this forum.

Let us know what you find out? I’d take mine to the local dealer but I have no confidence in them!

Bunker1 · June 8, 2020

Had the same problem first when starting my 2019 6.2 Sierra. Found the mouse to come back when the starter engages after starting from stopped at a light. I hate that feature too, wish there was a way to turn that feature off for good instead of hitting the button each time I drive it. Took the truck to the dealer for the squeaky belt, they did replace a belt, however the sound is still there. Hopefully they can figure this out.

AT-FORE · June 10, 2020

Update to my 5/26 post...

I finally got my Sierra 6.2 AT4 up to the dealer to take a look at the squeak. The repair mechanic seemed very knowledgeable and did a ride along so I could reproduce the issue. The squeak was very prevalent at autostart/stop and it happened right beside the building so he could very clearly hear it. Unfortunately he indicated it has to do with the compression exhaust valves which are associated to the AFM (Active Fuel Management) system and the cylinder deactivation functionality. He told me that given more people are buying these vehicles as "family vehicles" causing some give and take in vehicle functionality. Consumers want better fuel economy hence the squeaky exhaust valves, and active fuel management functionality and the super annoying autostart/stop. Apparently, consumers want a faster start/crank time, hence the buzzing when I open the door to prime the fuel pump. Regardless, I still cant believe GM would put a vehicle into production with this kind of squeak or noise... why not put a little more R&D into the valves so they don't squeak when used on a luxury truck? The mechanic also said installing an exhaust system WILL NOT solve the problem as the valves are right under the headers on the engine, still int he exhaust pipes but close to the engine. It seems the only way to get rid of this squeak would be to have someone deactivate the whole AFM system, which apparently can be done but voids warranties.

Well guys, I guess im driving a super bad ass AT4 with a "normal" loud squeak..... which I hear every time I drive it.... (headbang)

Jav_eee · June 10, 2020

It goes away after a few seconds of being started. Relaaaaaxxxx. It’s one of the characteristics of having a 6.2 idk

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STARK · June 10, 2020

My 2019 AT4 6.2 does the same thing...Did you find out what it was??

RST-stan · June 11, 2020

So glad to hear Im not the only one. I don't have a HC, just a regular ol RST. I wonder why it only does it on the auto stop for me, but not cold starts or even warm starts for that matter. Im failing to see what is actually squeaking tho, is this an oil pressure issue to the valve train?

19Sierra · June 12, 2020

Mine whistled everytime I accelerated. I wired the exhaust flapper in front of the muffler to the open position just for the heck of it and the whistle completely disappeared. I had originally thought it was a squeaky belt as well.

Edited June 12, 2020 by 19Sierra

todd308 · June 19, 2020

2020 AT4 6.2, <1000 mi, noticed the same thing, I don't notice it at stop/starts or during driving but I definitely notice it if the truck has sat say overnight or during all day at work. If it's just in/out of a store it's still quiet. But yeah, mine sounds just like a bad pulley/slipping belt for 15-20 seconds and then it just goes away. Haven't tried to investigate to see if it's the exhaust flapper as some have found.

It has a few gremlins so far

1) said squeal at startup

2) Hard/delayed shifts from 1st to 2nd and 2nd to 1st (read disabling auto start/stop can help, but haven't tried it yet)

3) For some reason the lane departure alerts that used to vibrate the seat have stopped, don't think I change any settings but some alerts like car/person behind still vibrate the seat

4) Even though it's turned on in the settings, autostart will not engage the cooled seats.

5) Traction control doesn't really appear to be working, if it's raining etc. the system says it's on but it doesn't seem to engage, IE it's easy to spin up the tires on a wet road turning a corner. Also even if I follow the steps in the manual, I don't seem to be able to turn both TCS and ECS off, it only seems to impact the TCS.

AT-FORE · June 19, 2020

todd308 - I have definitely noticed 1&2 on your list above. If you end up investigating the exhaust valve and determine that is not the issue definitely keep us updated. I know these trucks have very sophisticated drive trains. My transmission shifting has actually gotten better. Some random hard down shifting occasionally but nothing out of the ordinary. When I test drove it, I felt it shifted in very odd ranges and in times when I thought it shouldn't, but I think that is all part of the 10-speed transmission. Maybe I have gotten used to the shifting at this point but I feel that aspect has gotten better with miles and my driving style. I have about 1500 miles on it now. 3, 4 and 5 on your list I don't think I have had an issue with. If you think something should be working and its not I would surely take it back to the dealer. My dealership was very forthcoming about telling me to come back if I had any issues or questions.

Another "gremlin" on mine is the buzzing whenever any door is opened. I have researched this and I believe its the fuel pump priming, but my truck does it when any door is opened or even the tailgate is dropped after sitting for 15+ minutes. This is a very odd feature for a vehicle in my opinion.

Jav_eee · June 19, 2020

todd308 - I have definitely noticed 1&2 on your list above. If you end up investigating the exhaust valve and determine that is not the issue definitely keep us updated. I know these trucks have very sophisticated drive trains. My transmission shifting has actually gotten better. Some random hard down shifting occasionally but nothing out of the ordinary. When I test drove it, I felt it shifted in very odd ranges and in times when I thought it shouldn't, but I think that is all part of the 10-speed transmission. Maybe I have gotten used to the shifting at this point but I feel that aspect has gotten better with miles and my driving style. I have about 1500 miles on it now. 3, 4 and 5 on your list I don't think I have had an issue with. If you think something should be working and its not I would surely take it back to the dealer. My dealership was very forthcoming about telling me to come back if I had any issues or questions.

Another "gremlin" on mine is the buzzing whenever any door is opened. I have researched this and I believe its the fuel pump priming, but my truck does it when any door is opened or even the tailgate is dropped after sitting for 15+ minutes. This is a very odd feature for a vehicle in my opinion.

That’s just what they do. The pump primes. They ALL do it.

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