Exhaust Rattle on 2021 6.2l CC

[Hkb82]

Tested it in manual mode on L9 and I couldn’t hear the noise so I’m almost positive in my case it’s the dfm doing it. To think it’s going to cost 600 Canadian for a pulsar lt to disable dfm really bugs me. Atleast it will also take care of the auto start stop issue and a few others. I really just hope it won’t affect any warranty issues down the road. 

[ChevyJoe85]

I just bought my 2022 Trail boss  6.2 and it's doing it...I crawled underneath and it's the flapper...i turned it by hand and put pressure on it and the sound went away...theres no way it should sound like that !! These trucks are big money !

[ChevyJoe85]

On 8/31/2021 at 1:05 PM, rsimons said:

I have the same problem on my 2021 6.2L Sierra Denali.  1st time I took it to the dealer they said it was the flapper valve and it was normal.  I then installed a Magnaflow cat back, but it still does it.  Took it back to the dealer and they said they drove another one that made the same noise so it's normal.  I asked what it was and they said they don't know.  It sounds like an exhaust leak, but they said there where no leaks.  It does it bad at cold start, and also on decel, right before you come to a stop.  Also, sometimes on light acceleration.  

Theres no way that's normal, that's total BS. Mine does it in park. It's the flapper. I crawled underneath and manually adjusted it with my hand and put pressure on it and it went away ! No excuse for this ! Big money trucks !!!