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Another bad valve thread

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?
Talking to my service guy he stated that trucks using "DFM" will not have this problem. Just trucks with "AFM".
 
Got the truck back today.
No. 8 cylinder valve was collapsed.
16 valves replaced, 1 guide, 1 rod and other various pieces.

I'm older but I remember in my "younger" wrenching days there are only 2 valves per cylinder.
He said they replaced them "all" did he mean all 8 cylinders ???

Also my parking sensor was not working.
One of the sensors in the front bumper was damaged.
I remember hearing a rock it while on vacation a few weeks ago.
Sensor = $42. Paint and labor = $350.
It had to be painted by the body shop to match the bumper.
 
So Ive been trying to collect Information on these lifter issues. curious people that are experiencing this issue.

1. Do you leave the Auto Start/Stop on ?
2. When did you do your First Oil Change ?
3. DFM/AFM disabled ?
4. 5.3L or 6.2L ?
5. Valve Issues ?
 
Last edited:
Got the truck back today.
No. 8 cylinder valve was collapsed.
16 valves replaced, 1 guide, 1 rod and other various pieces.

I'm older but I remember in my "younger" wrenching days there are only 2 valves per cylinder.
He said they replaced them "all" did he mean all 8 cylinders ???

Also my parking sensor was not working.
One of the sensors in the front bumper was damaged.
I remember hearing a rock it while on vacation a few weeks ago.
Sensor = $42. Paint and labor = $350.
It had to be painted by the body shop to match the bumper.
I have to make a correction on this post.
No. 8 cylinder lifter was collapsed not the valve.
Also the shop replaced all 16 lifters, not valves.
I've heard GM is now replacing all lifters regardless of mileage and damage.

To answer your questions JDenham
1. No
2. 7000 miles
3. No
 
So Ive been trying to collect Information on these lifter issues. curious people that are experiencing this issue.

1. Do you leave the Auto Start/Stop on ?
2. When did you do your First Oil Change ?
3. DFM/AFM disabled ?
Id add:
5.3 or 6.2 engine?
 
1. Do you leave the Auto Start/Stop on ?
On
2. When did you do your First Oil Change ?
6000mi
3. DFM/AFM disabled ?
No
4. 5.3L or 6.2L ?
5.3
5. Valve Issues ?
No
6. Current miles?
8000
7. Model year
2021
 
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?
Just had mine replaced 2 days ago. The day after picking it up the CEL started flashing again . Taking it back on Monday for round 2.
 
So is this an issue on just the DFM cylinders and is it DFM that is somehow causing it, or just defective parts on those (different) cylinders?
It's been talked about everywhere that de-activating DFM keeps these lifter(valve, pushrod, whatever ends up breaking or bending when a lifter presumably collapses and it shouldn't or vice versa) issues from happening.

If this is the case, doesn't using tow/haul or sport mode also turn off DFM? Good backwoods way of keeping the issue form happening, always use T/H or Sport mode?

Asking because my 2020 5.3 is in the shop, 20k miles. Dealer saying, not module/computer related, not trans, not injectors or sparkplugs causing a misfire, but it's fugged up! Now they're heading into the engine. Didn't say lifter issue afaik. (I'm getting second hand info as our equip manager is dealing with it.)
 
1. Do you leave the Auto Start/Stop on ?
Truck didn't come with it
2. When did you do your First Oil Change ?
5500 - Oil life was 18%
3. DFM/AFM disabled ?
Yes - Pulsar LT since 5500mi on truck
4. 5.3L or 6.2L ?
6.2
5. Valve Issues ?
No
6. Current miles?
8800
7. Model year
2021
 
2020 5.3L w/ 17,000 miles. Had a lifter failure on October 27. I requested both banks to be replaced and dealership agreed. Because of parts shortage, it took 3 weeks to complete repair. When I picked it up yesterday, they had only replaced 1 bank and gave me the runaround about parts shortage prevented them from replacing both banks of lifters. After meeting with service manager to express this was unacceptable, they agreed to order the other bank of lifters and parts and will call me to bring the truck back in when parts arrive. 20 miles from the dealership, the check engine light came on (with all the other alerts) and truck began misfiring, shaking and sputtering like it did with initial lifter failure. Had to have it towed back in this morning. I absolutely love this truck, but I’m about over it. It’s like driving a ticking time bomb.
1. Do you leave the Auto Start/Stop on ?
I usually turn in off
2. When did you do your First Oil Change ?
5000 miles
3. DFM/AFM disabled ?
No
4. 5.3L or 6.2L ?
5.3
5. Valve Issues ?
Lifter failure
6. Current miles?
17,000
7. Model year
2020
 
So Ive been trying to collect Information on these lifter issues. curious people that are experiencing this issue.

1. Do you leave the Auto Start/Stop on ?
2. When did you do your First Oil Change ?
3. DFM/AFM disabled ?
4. 5.3L or 6.2L ?
5. Valve Issues ?
1. I leave it on, but it rarely works.
2. First oil change @ approx 2000 mi, then by oil life indicator.
3. No
4. 5.3
5. No valve issue supposedly, but 2 collapsed lifters on same bank @ 19k miles. Unsure of which cyl or same cyl, not my truck, don't have the paperwork from the dealer.
 

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