Lz0 weird screeching noise.

Yeah I haven't gone to the dealer yet. Eventually it will go. If whoever has the noise goes in before I can update with my results please feel free to post about it.

As for that report of the whole tank of def fuel is used in 1500 miles that's crazy high. I had 2500 miles it did take the 2.5 gallon jug and I started towing my single car enclosed trailer at 1200 miles right after I did my first oil change. and the trailer is heavy. I get a notification in my cluster saying I may be above the max carry weight. Which I think is very weak sauce. Power wise this truck pulls like a dream for what it is. Much better than my 6.2 with max tow. Suspension wise there is a lot of areas that defiantly need beefing up.

Seems like an Idash is a must have for these trucks. anything else recommended out there?

Another thing I notice about this truck is the idle seems to rise at random times to like 900 from 700. It happens way to often to be regen. like a few times a day. driving 60ish miles by the end of the day.. and my def is still showing full. but maybe its just doing regens that often?

doug13 said:

Based on my experience you are going to get a print out of a tech bulletin that says everything is a-okay

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You are correct! Got my truck back yesterday and basically said no active CEL, cleared system and everything checked out. They said that it could have been bad fuel, which could be because before the CEL I put 10 gal in from speedway to get me through the weekend until I got to my usual gas station.
As far as the buzzing from the exhaust valve, they said they couldn't reproduce it so nothing they could do about it. They'll leave the ticket open and bring it back if its more constant and can be reproduced.
They had it for almost 3 days, at least they put me in a loaner.

Any updates from anyone on the buzzing sound?

Had mine at the dealership yesterday. They confirmed the rattle/buzzing. I found someone else online who had the exact same video of what mine is doing, coming from the same place and he posted his repair invoice after his dealer warranty fixed the issue(see below). I brought this to the dealer, they were appreciative of the starting point. They said they had to open a case with GM to proceed, waiting to hear back. I will post updates from my invoice once it is hopefully resolved so everyone can use it as ammunition to get it fixed.

edeering03 said:

Had mine at the dealership yesterday. They confirmed the rattle/buzzing. I found someone else online who had the exact same video of what mine is doing, coming from the same place and he posted his repair invoice after his dealer warranty fixed the issue(see below). I brought this to the dealer, they were appreciative of the starting point. They said they had to open a case with GM to proceed, waiting to hear back. I will post updates from my invoice once it is hopefully resolved so everyone can use it as ammunition to get it fixed.

View attachment 3677

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Thank You.

I am actually at the dealer or right now as we speak finally getting the time to bring it in. Seems like the previous post hit the nail right on the head. I will update what they do with my truck when I have an update.

Gcmfishin said:

I am actually at the dealer or right now as we speak finally getting the time to bring it in. Seems like the previous post hit the nail right on the head. I will update what they do with my truck when I have an update.

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Any update? Still waiting for my dealer to get back to me on the claim with GM

edeering03 said:

Any update? Still waiting for my dealer to get back to me on the claim with GM

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Well while i was there. the service advisor heard the issue said he has never heard that issue before i would have to wait for the diesel tech to look at it but since i am in fort Lauderdale Florida which just had a flood the diesel tech was to busy with other trucks that were damaged in the flooding. so they said i would leave the truck for diagnostics. and they didn't have a loaner. so I said I don't have time for that. i think i am just going to order that part and change it out myself. waiting for the dealer to do anything is for the birds. i also have the rear end thump from the leaf springs now and the service guy is familiar with that issue but again said they are backup and cant do anything as the have to hear it them selves. and they they have to go through steps that just wastes a bunch of time. before they replace the leaf pack. so annoying my last gmc Sierra and i said i wouldn't buy another one. but due to its the only 1/2 diesel option kind of stuck with it.

I need to due some research on the exhaust valve thing. cause i rather remove it all together. its restrictive imo.

Update on this. Went to a second dealer since the first was giving me the run around for months. I sent them videos of mine making the intermittent rattling/buzzing noise. It only occurs on my truck once its warm, especially when towing while at idle. They opened a case with GM engineering (stated GM has 2 days to get back to them once the case is opened). Engineering confirmed it is the valve within the exhaust assembly making the buzzing noise. Dealer ordered a new exhaust and I'm waiting to get it installed. My dealer wasn't able to replicate the noise after idle for a few hours but they sent my videos in and that was enough. Moral of the story is the dealer CAN help you...just depends on the dealership. Will provide an update once then new exhaust is installed.

One of the things that changes engine idle RPM is the charging voltage to the battery, the ECM may raise the RPM if it detects the battery needing more charge. (Somewhere in the owners manual) There may be other reasons for an increase in RPM?

Andystoy AT4 said:

One of the things that changes engine idle RPM is the charging voltage to the battery, the ECM may raise the RPM if it detects the battery needing more charge. (Somewhere in the owners manual) There may be other reasons for an increase in RPM?

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Its not an increase or change in RPM...the valve inside the exhaust is resonating / causing an intermittent buzzing sound....

Gcmfishin said:

Yeah I haven't gone to the dealer yet. Eventually it will go. If whoever has the noise goes in before I can update with my results please feel free to post about it.

As for that report of the whole tank of def fuel is used in 1500 miles that's crazy high. I had 2500 miles it did take the 2.5 gallon jug and I started towing my single car enclosed trailer at 1200 miles right after I did my first oil change. and the trailer is heavy. I get a notification in my cluster saying I may be above the max carry weight. Which I think is very weak sauce. Power wise this truck pulls like a dream for what it is. Much better than my 6.2 with max tow. Suspension wise there is a lot of areas that defiantly need beefing up.

Seems like an Idash is a must have for these trucks. anything else recommended out there?

Another thing I notice about this truck is the idle seems to rise at random times to like 900 from 700. It happens way to often to be regen. like a few times a day. driving 60ish miles by the end of the day.. and my def is still showing full. but maybe its just doing regens that often?

Click to expand...

My reply was to the question about idle RPM changing on this post, so I copied the post for clarification.

Andystoy AT4 said:

My reply was to the question about idle RPM changing on this post, so I copied the post for clarification.

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Understand now. The thread isn't about RPMs or DEF usage, plenty of other places for that on this forum it probably shouldn't be put in here. Just trying to document this exhaust rattle/resonance issue and resolution since there are now quite a few cases of people experiencing it

edeering03 said:

Update on this. Went to a second dealer since the first was giving me the run around for months. I sent them videos of mine making the intermittent rattling/buzzing noise. It only occurs on my truck once its warm, especially when towing while at idle. They opened a case with GM engineering (stated GM has 2 days to get back to them once the case is opened). Engineering confirmed it is the valve within the exhaust assembly making the buzzing noise. Dealer ordered a new exhaust and I'm waiting to get it installed. My dealer wasn't able to replicate the noise after idle for a few hours but they sent my videos in and that was enough. Moral of the story is the dealer CAN help you...just depends on the dealership. Will provide an update once then new exhaust is installed.

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Good morning, did this fix the problem? I am trying to make sure to point my local dealer in the right direction instead of saying "its normal" or "they all do that" Thanks!

edeering03 said:

Had mine at the dealership yesterday. They confirmed the rattle/buzzing. I found someone else online who had the exact same video of what mine is doing, coming from the same place and he posted his repair invoice after his dealer warranty fixed the issue(see below). I brought this to the dealer, they were appreciative of the starting point. They said they had to open a case with GM to proceed, waiting to hear back. I will post updates from my invoice once it is hopefully resolved so everyone can use it as ammunition to get it fixed.

View attachment 3677

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Had my truck in for service to replace a particulate matter sensor and also had them look at the exhaust buzzing again. They had contacted GM on a prior visit but described the noise was coming from the trans oil cooler? But this trip they ordered part 87829082 - Pipe 3.609. Noticed they ordered an actuator, not sure if it’s related to the sensor replacement or the buzzing. Hopefully this will get rid of the buzzing.

12/21/23 Update - got the truck back from service. So far so good… no buzzing after 35min ride home. Hopefully it stays this way.