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Another bad valve thread

DonJinIA

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It's official, I've been added to the list of TB owners with bad valves.

2021 TB purchased in Feb 2021. Build date was Jan 2021. 14,700 miles.
Truck started running rough a few days ago, lots of warning lights flashing, ESC, Parking Brake, ABS etc...etc.
Wasn't able to get it to a dealer until today.
He called this morning and said my valves and lifters need to be replaced.
He verified there is a service bulletin out about defective valves.
Low mileage trucks, GM is now saying to replace all valves and lifters.
Dealer said my truck qualifies as a "low mileage" truck.
Repairs will take until later next week.
Dealer said he has to overnight more parts, there are 3 trucks ahead of mine with the same issue.

Curious if anyone has had issues after their valves/lifters had been replaced?
 

steig

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Wow, that shouldn't happen to a 14,700 mile vehicle.
 
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DonJinIA

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It’s all the 6.2’s that have those issues unfortunately
I've got a 5.3.
Most of the ones I've been hearing about are 5.3's.
I actually was kind of relieved.
I was expecting a call saying a computer module was bad and it would take months to get a part.

I do have a bumper to bumper extended warranty to 100,000 miles, so I'm not too worried about it but the inconvenience is a pia. :)
 

Jmzvet

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A warranty is great but still sucks to break down 200 miles from nowhere Texas with 3 kids in your $60k truck👎
I put over 200K on a 2008 Suburban 5.3 with AFM and had no problems.
I’d like to see a breakdown of the model years and engines affected.
If it’s all 2019-21s then it’s not a
“Bad batch” of valve springs. It’s a design flaw affecting all 5.3 and 6.2s with DFM.
I’m guessing they use the same springs?
 

Indy1982

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Bought 2021 Trail Boss March 19, 2021. On September 18, 2021(1 day till 6 month ownership) at 6363 miles with cruise set vehicle slows to 62 all warning lights lite up vehicle won’t go past 62mph. Made it to dealership won’t find out till Monday the problem. From other reads sounds like lifter failure. Ugg
 

tommysf13

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I have seen now deleted mechanic clips warning about newer vehicles in general having problems as a result of covid. Vehicles were built but sat until sales were opening back up. The new seals and other parts get no use or lubrication while sitting. True or not it sounds very probable.
 

TrailBoss

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Most of the ones I've been hearing about are 5.3's.
I actually was kind of relieved.
I was expecting a call saying a computer module was bad and it would take months to get a part.

I do have a bumper to bumper extended warranty to 100,000 miles, so I'm not too worried about it but the inconvenience is a pia. :)
What the.. That is no joke the first time I’ve heard about it being on the 5.3’s too.. In my horrible defense, my friends say I live under a rock.
 
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DonJinIA

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Bought 2021 Trail Boss March 19, 2021. On September 18, 2021(1 day till 6 month ownership) at 6363 miles with cruise set vehicle slows to 62 all warning lights lite up vehicle won’t go past 62mph. Made it to dealership won’t find out till Monday the problem. From other reads sounds like lifter failure. Ugg
FWIW I asked the dealership if it was a lifter problem.
The service manager said it was a valve issue.
Service guy said the valves are sticking.
This causes the lifters to fail.
I'm "assuming" the valves are oversized causing them to hang up.
 

Trail Brian

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The valves are bending and lifters are collapsing due to misfires on AFM motors. (Active Fuel Management) ...the newer version DFM (Dynamic Fuel Management) which is different as it has 17 different possible cylinder deactivations rather than a set 4.... we know this is how GM boosts the MPG ....they also claim that they had a bad batch of lifters from 09/01/20 to 03/21/21.... I do know that it's not uncommon for a misfire to bend a valve or pushrod for that matter( whether its faulty or not) .. the modules that deactivates this feature from what I have read isn't available yet for 6.2 with 10 speeds. (Range Technologies') .. I'm still researching... from what I have learned so far the module will void warranty but I'm chasing that down as well... why it only happens on some and not a majority is a mystery....the internet has a tendency to make things bigger than they are.... I'm concerned because I'm heading back to the Baja for a few months and obviously don't want to get stuck...I did find it interesting that GM is discontinuing this feature for now because of the unavailability of the "chips" needed to MFG this technology ? I love my trucks but I really wish GM would step up and say HEY ! bring your truck in for this issue and call it a recall and fix the problem... I am going to call a few Service managers and ask If we can deactivate this feature without voiding warranty.... or maybe the majority will be fine and I/we shouldn't worry ...... I have 8200 Miles on my rig
 

Jmzvet

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My 5.3 was built 12/20. Im right around 7000 miles. It seems to be more prevalent on 6.2s? Also seems the more miles accumulated, the likelihood of the lifter problem diminishes? These are just my observations and I may be incorrect.
I really like my truck but this is concerning to me.
 

Trail Brian

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My 5.3 was built 12/20. Im right around 7000 miles. It seems to be more prevalent on 6.2s? Also seems the more miles accumulated, the likelihood of the lifter problem diminishes? These are just my observations and I may be incorrect.
I really like my truck but this is concerning to me.

The DFM is supposed to be an improvement ? only from what I have read no first hand knowledge ...I will say this my 5.3 (2018) was bullet proof at 66 K before I traded (28.6 MPG was my best for at least 50 miles, 3.08 rear end) .... I agree the likelihood diminishes with miles.... I think you and I maybe over the hump... fingers crossed...:)
 

TrailKruk

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I have a 2021 LT 6.2 Midnight Trail Boss I bought in Feb built in Jan. I mostly ran in L9 (no DFM) until I installed the Pulsar (perm no DFM) a month or so back. Seeing as I'm now at 9500 miles it seems I'm still very much at risk compared to OPs 14k. So my question is are these trucks safe to drive? The wife and I typically are in the UP without cell signal and possible surrounded by meters of snow. If the spring/lifter problem happens when I'm say around Whitefish Point in January, are we just going to be snowshoeing for miles (read: dead) or will the truck get us somewhere safe?
 
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DonJinIA

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Spoke to my service manager today, my truck is still in the shop.
Truck could possibly be done tomorrow.
They are replacing all valves and lifters on the AFM cylinders.
He stated that the valves on the 4 AFM cylinders are different than the ones on the other 4 cylinders.
The AFM cylinder valves have the known defect.
GM is now advising to replace all AFM valves on vehicles below a certain mileage. Mine has 14,750.
I don't know the magic mileage number. My best guess is 36,000.
He also confirmed that not every truck has this problem.
The percentage is actually pretty low compared to how many trucks are on the road.
He also stated that there have been no return repairs.

A little more background on this. At around 4000 miles I had a random misfire.
Check engine light came on, I cleared it with my OBDII reader.
Happened again around 5000 miles, again I cleared it.
Changed gas stations and never had the problem again.
Went in for my first oil change and informed the service department of the 2 random misfires.
I assume they cleared the permanent codes and everything looked ok to them.
Looking back now, I'm assuming this is when the valves began to "stick" fail.
 
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