GM's AFM, the Good, the Bad, and the Ugly
 

If you have a GM powered truck with AFM (or DFM for the later engines) and it's hasn't "lunched" a cam/lifters or you've lost some rod or main bearings consider yourself lucky.

The failure rate is high with those engines and don't think you are OK with the more recent DFM engines where they were supposed to have made changes to improve that deal.

The info I'm providing here are straight from two good friends of mine. One is the lead mechanic for over 30 years now at a dealership, the other a service writer at another dealership.

They have nearly new vehicles sitting out back of their dealerships waiting on engines. The supply has ran out and they have even went into the used market and exhausted that supply as well. One vehicle in particular was a pretty new 2500HD with the bigger 6.2 engine and it's been sitting out back several months waiting on an engine.

I already knew AFM was a chit set-up and have used tuners to disable it on several vehicles I've worked on and owned. AFM or the early version cancelled the inner 4 cylinders and eventually they start pumping oil if you keep it long enough. The newer DFM system is sequential but still prone to lifter failure(s) and wiping out camshafts. The newer engines are also experiencing main and rod bearing failures.

Not sure how all this is going to sort itself out? According to a quick Google search it's reported that a Class Action Lawsuite has been filed. I also read where GM is recalling some vehicles to upgrade the lifters. In any case it will be interesting to see how all this sort itself out........

I have AFM on my 2011 Camaro. It worked seamlessly. The only thing I didn't like was an obnoxious tone from the exhaust when it would switch back to 8 cylinders. I have aftermarket exhaust. So it's more noticeable. I disabled it shortly after buying the car. It had 23k on it when purchased. It cost me about 1-1/2 mpg. I'm more than willing to give it up. Car now has 145k on it and runs perfectly. This goes back to the K.I.S.S. program. Nothing more complex is less prone to failure.

I think we are seeing how poor our supply chains are and also the cost cutting that OEMs are having to go after from many geopolitical pressures.
Stellantis has a run of blocks cracking and other ailments so it’s not just GM.

Yeah my Avalanche 6.0 wiped out a bearing with only 115k on odometer and I changed oil on a consistent basis. The rebuilt motor I have in it now is a AFM delete so different lifters and vlom. I suspect this is what most people are doing once there vehicle is out of warranty. As Cliff mentioned it can be disabled with a tuner program as well if you do not want to go full AFM delete. Overall these LS motors are still the most versatile engines out there.

So I used. to work for GM customer service. I can tell you the more recent the vehicle, the higher number of catastrophic failures I saw. Before I left a few years ago, they were having issues with several new vehicles on both engines and transmissions. It was eye opening. In just 3 short years, I saw a drastic increase. I. am sure it is across the board for all manufacturers, but I only have personal experience with GM.

I have a 2015 GMC 2500 4WD,84000 miles.Extended cab and 8 ft bed. Should I be looking at anything? I've bought the extended warranty when new and kept updating. Good friend says I'm wasting my money.

I had no idea about that when I got a new 2023 Silverado 5.3. Once I learned of the issue, I was concerned. Unfortunately, the truck was lost in a fire. So, after much research, I replaced it with a similar 2024 Silverado with the 3.0 Duramax LZ0. This is the best one ever of the 7 Silverado's I've owned. Drives smooth, 10 speed trans works good, 27-31 mpg (yes) . The 3.0 diesel is only a $995 option over the standard gas v8.

I have heard and seen some failures. I have a new to me, 2021 Suburban with a 10L80 and a 6.2 V8. i bought it a month ago at 77,000 miles. It runs great and you can't tell when the DFM is active. I checked warranty history, I work for GM, and it is the original engine. Never had an engine service history. It is not as easy to remove the DFM on the LT engine. 2021 and up have the Global B electrical architecture. Not as easy to get a tune or modify it.

I have owned a few GM SUVs with both the 5.3 and the 6.0 and 6.2 engines.I have a friend also is the service manager and his advice was to change the oil every 3000 and will lessen the chance of lifter failures.So far have not had one issue.My 2017 Yukon has 90K miles and my 2019 Escalade has 50K.FWIW,Tom

I formerly ran a business which primarily did LS engines. More than half of the work was lifter failures....plenty of AFM's which we would do a delete 99% of the time...but way more LS1, LS2 and LS3 standard GM lifter failures. Scarred me so much I still run flat tappets in my pontiac's and only recommend oil pressure fed bushed rollers for anyone I help out that wants to go roller in old school V8's.

And these lifters have been around for 17 yrs or so.

Well ... I'll have to give the 5.3 a vote of confidence. My 2011 has 110k on it now and purrs, still an extremely quiet engine. I've thought I've felt the AFM system kick on/off maybe a dozen times in those years, I've never heard a change in exhaust note. It's got probably 30,000 miles of towing, 6,000 lbs or less. Full tow package, HD cooling etc., 3.55 (approx) rear end. Nothing but Mobil 1 it's entire life. Got new plugs, wires, alternator, coolant, fuel pump and some evap components at 100,000. Nothing was wrong, just preventive replacements. Never thrown a single code (knock wood).

Wonder if driving style, or type of driving effect the longevity with the AFM system. Seems like it would kick on most of the time on the highway .. 80% of my highway miles have been towing where it probably doesn't trigger the AFM much at all. The truck has been used primarily for medium length local travel in situations where the AFM doesn't have much of an opportunity to stay on for long.

Brakes really suck though.

Geez Fuel-Injection cutoff of power-balanced pairs or a Quad could have won the compare against AFM, but the oxigenated exhaust and O2 sensors would have caused the need for a separate exhaust path. Would have been worth it.

Mechanically, these systems work smoothly and are reliable in millions and millions of miles. The software continues to improve. The problem is the QUALITY of that hardware, the vendors making the parts and the pressure applied by GM to take more and more money out of the parts. The results are loose tolerances, poor finishes, lower quality metals, poor heat treating, the list goes on and on. Then the failure rate creeps higher and higher. I have anecdotal evidence of AFM engines running over 300,000 miles with no issues. And others failing at 30K. You pay your money and take your chances. It's an unfortunate gamble. My wife currently has a Mazda 4-cyl that runs on 2 cylinders under certain conditions to save fuel. It is so smooth changing from 4-cyl to 2 cyl mode, only a tiny change in exhaust note can be detected. It's an SUV, non-hybrid, AWD vehicle that gets 35-37 MPG on the highway all the time. But they are having the same issues with the engines as GM. But not all of them. Hit or miss. An extended warranty that covers this system might not be a bad idea for people planning to keep these vehicles for the long haul.

Few years ago I flew back to MA from FL. I flew into PVD because it's closer to my parents home than Logan. My dad picks me up in my mom's new 2022 Tahoe with the 5.3. It's got 4K miles on it.

As we get close to I495 the truck shuttered and the dash lit up like a Christmas tree. Flashing check engine light, everything. I mention to my dad that's bad. He just shrugged and mentioned it's under warranty. It's got the idiotic start/stop feature. So as we get close to the house we have to stop at a light. Truck turns off. I said I hope it turns back on because we had to stop at the off ramp of the interstate. Thankfully it started back up and all the lights went off.

Get the truck home a few seconds later and park it. He had to go pick up my niece at her horse riding so I called the dealer. They tell me to use OnStar to schedule a tow.
I do that. Tuck comes and picks it up and takes it to the dealer.

Few weeks later my dad calls me and says it's fixed. Few of the lifters were bad. Replaced all the lifters, new head gaskets, etc. GM gave my parents an extended powertrain warranty to 100K miles. GM knows it's been a big problem. But thanks to the idiots who want all these fuel economy standards this is what you're going to end up with.

They will never be as reliable as the old LM7 that I still have. But, my brother has a 2007 5.3 with AFM that has 138,000 miles. Runs like a clock. Very quiet, no oil leaks, etc. My co worker has a 2010 Tahoe with those lifters. Same thing. It has close to 200,000 miles. Absolutely quiet when it runs and dry as a bone as far as oil leaks.


So, for all the failures,[even though there are many more than the past] how many are running around with no problems?


It`s not stopping me from buying a 2025 truck with the 5.3 for retirement.;)


I will run 5w30 instead of the 0w20 they call for. Funny how they call for 5w30 in the 4.3 and 6.6, and some vette and camaro 6.2`s. 0w40 in others with the same parts. Course, I`m starting from NEW.



It`s all about CAFE.;)


By the way, the AFM versions have an oil screen in the valley tray to keep trash out of those lifters. If it`s dirty, it will cause a drop in pressure to those lifters. So, if ya got one, change it.


https://www.melling.com/wp-content/u...s-3.1.18-1.pdf



DFM has a different block without all the stuff in the valley tray.


They don`t call it a valley tray but hey, this is a Pontiac forum after all.:)

I have a 2018 GMC Sierra with almost 50,000 miles on it and did not even notice the AFM until about a month ago. I saw that the V8 icon on the dash would change to V4 and that is when I found out I had the AFM. If it weren't for the icon on the dash I would have never known it. That's how technologically advance I am.

2018 Silverado with 5.3

28K miles without issue so far. I follow Chevy's maintenance schedule with dealer service only.

Reading this thread creates anxiety. This forum creates anxiety about valve lifters in general.

The performance and mileage are excellent. The system works.

I'd love to hear statistics. Anyone have factual failure rates? Any correlation with usage model - ie city vs highway, start/stop cycles, towing, etc.?

Anyone actually purchase extended warranty coverage on this? Anyone with extended coverage that used it?

With all these complex engines today, pick your poison. They ALL have problems. Even the mighty Toyota.