As GM Authority readers are likely aware, Dynamic Fuel Management (DFM) – GM’s second-generation cylinder deactivation technology that disables a vehicle’s cylinders in the name of fuel economy – is commonly associated with V8 engine issues in the Chevy Silverado 1500 pickup, along with the Chevy Suburban or Tahoe SUVs. Though never officially confirmed by GM, DFM is most commonly associated with power loss, excessive oil usage, and damaged valvetrain components, among other issues. Those looking to disable DFM can opt for a device like the DFM Module from Range Tech, but those who don’t have one can disable DFM using a little-known trick.
The trick is to use the paddle shifters to shift the vehicle’s transmission into ninth gear, otherwise known as L9. This is the only gear where the Engine Control Module (ECU) disables DFM in stock vehicles. Plus, as a benefit, L9 also disables Automatic Stop-Start, which shuts off the vehicle’s engine when it comes to a complete stop, such as at a stop sign or stop light. By comparison, every other forward gear from first to eighth, along with tenth speed, keeps DFM enabled. For instance, L10 has DFM active, while keeping auto stop-start off.
So if you don’t want DFM in your Chevy Tahoe or Suburban, or the Chevy Silverado Light Duty, but haven’t had a chance to get a DFM defeat device, then driving in L9 is your only hope.
As a reminder, DFM succeeded Active Fuel Management (AFM) in GM’s Cylinder Deactivation technologies with the introduction of the 5.3L V8 L84 engine and the 6.2L V8 L87 engine. DFM is capable of disabling as little as one and as many as seven of the engines’ eight cylinders, creating multiple “operation patterns.” By comparison, Active Fuel Management is capable of shutting down only half of an engine’s cylinders, or none at all – thereby having only two operation patterns.
Introduced in conjunction with the 2019 Silverado 1500 before making their way to Tahoe and Suburban stating with the 2021 model year, the 5.3L V8 L84 and 6.2L V8 L87 engines are part of GM’s second generation EcoTec3 engine family. Both feature an overhead valve (push-rod) configuration with aluminum blocks, Direct Injection and Variable Valve Timing. The 5.3L is rated at 355 horsepower and 383 pound-feet of torque while the 6.2L makes 420 horsepower and 460 pound-feet.
Comments
AFM/DFM not a reliability issue. Falsity being spread by those who don’t want Chevy engines being sold. Fact is more AFM chevy engines get pulled for builds than any other engine, Ford, Toyota or Honda as a testiment of their durability. Only AFM engines with issues AFM related was the LC9 5.3. and that was almost always due to poor oil. Hemis has thin oil that would chew cams, but that was regardless of if it was an AFM engine or not. The GEN V engines have had no issues with AFM any more than issues with bearings/valves/VVT or standard lifter tic, and that’s a statical Fact! Please no stupd anecdotes “Oh my new AFM engine failed after 5 days” as no one here will believe it.
Now for another statistical fact, AFM engines actually last longer. GEN V small blocks are showing significantly less wear upon rebuild. When AFM allows the engine to run more efficiently, you have less heat, less fuel wash, thus less strain on the oil. Multiple rebuilders rebuilding Gen IV/V small blocks note less bore and ring wear on AFM engines VS your typical SBC/Big block or Gev III.
AFM is the new catalytic converter, where everyone blames it for all the issues even though it has next to no cause for any of the problems. Example? Current 6.2 engines would still fail even with AFM mechanically deleted, as the oversized lifter bores don’t care if your an AFM lifter, hydraulic roller, or solid Tappet lifter. It’s going to wear out.
That’s great, except for the small fact that DFM ≠AFM.
One is more complex than the other. How many engines with DFM are being “pulled for builds”? Not that many.
Wow. You are so misguided. Ask any Chevy mechanic and they will tell you AFM and DFM are terrible for engines. 2 of the head mechanics at my dealership both stated this. My father is a retired mechanic of 35 years and also state’s this. I’ll take his word on this. If you go to GM trucks.com amd do a quick search you will see this is an issue. Ford offered cylinder deactivation on their 5.0 V8 and have had all kinds of issues. Go to some of their forums as well.
TNT, I went to my dealership and asked their head mechanics, they said it isn’t really a problem at all if you keep up with maintenance and don’t have one that fell in the 3rd party manufacturing issues. See how easy it is to lie on the internet? Facts are much less failed than you want to lead others to believe. Yes it adds to some complexity, and yes there have been some failures solely due to it, but many have been to neglect (can’t put that on GM) or failed 3rd party manufacturing issues that were later caught. Once you take those out of the equation, the failure rate is in the decimal of a percent. So no, they aren’t “terrible”, not even close. Same with stop start.
@TMI
So we are supposed to “believe” your mechanic just because you said so!?! But my 2 mechanics I use at my dealerships are liars, and not afraid to speak their opinion and it’s false?!? See how easy it is to manipulate the wording…..you are too fake and full of $h!t, it’s laughable! You try WAY to HARD to one up me, yet, you fail
Yeah, hence this whole time I’m point out the fact that LS engines are the #1 for swaps. Everyone “knows” a mechanic or is one on the Internet, but let’s look at indisputable facts, 1, the LS/LT is #1 engine for swaps no contest. 2, there are more used LS cars on the road today than any other OEM, 3, Chevy V8’s command higher return value than Ecoboost or any other engine except Toyota V8’s, which they aren’t far behind.
I conceed that there will be some issues given the shear volume of the number of these engines sold , 6-7 times that of toyotas V8’s, there will be issues, there will be engines that are abused to no end that end up failed under 100K miles, but by far, you’ll see many older Chevy V8 trucks and cars on roads where Toyota 4 cylinders have long given up the ghost. All V8’s under 15 years old (with the exception of the HD’s, and a couple 2020/21’s) have AFM/DFM, and are doing just fine, better than all their competitors.
Those are the facts. From that I surmise that AFM isn’t the issue.
Other than an AFM V8 engine sees the mechanic way less often than a DOHC 4 cylinder from any OEM. Lifter tic also is a common occurrence on engines of all makes and model that go too long without an oil change. How is An AFM engine coming in for lifter work at 150K any different from a DOHC coming in for lifter tic at the same milage?
Note, it’s not. The Chevy V8’s are reputably more reliable than any other V8 out there, and almost every I4 or V6. And every Chevy V8 since 2011 uses AFM. Most since 07 use AFM. How many spare Coyotes, 5.7 Toyota do you see running around used? Every one gets gobbled up for replacement in current bodies.
Hate to break it to you but any small block V8 before 2007 and AFM, lasted longer and didn’t have lifter failures like the 07-25 models do. Doesn’t take a rocket scientist to correlate the problemThat’s just the facts!
He is correct . Mechanics and Forums really have messed up this engine with false statements. LEAVE the DFM AFM alone if you disable it the oil passages will eventually gum up because of no oil flow. The LIFTERS collapse and cause big problems. The old tale that it was bad was because the owners didn’t change there oil on time and the small passages would clog causing problems. Now we have a new problem with people who disable. These engines are complex with lots of passages and need there oil changed every 3k. We have seen just as many failures with the AFM removed as Kept. All the users who just change there oil on time every 3-4k will make there engines last to 500k but you need to change your oil!
Steve : Perhaps you’re employed in engine R&D for GM ? Pity you, friend.
Proof please
Our local dealership has had little to no lifter issues on DFM vehicles that have had oil changed at 5,000 miles or less. Stretching the oil changes drastically increases the chances of something happening.
I just had to get a new engine in a 2017 Sierra 6.2 with 87K miles due to a failed lifter. As soon as I picked it up, the starter failed. Definitely a quality control issue at GM & was not covered under warranty.
You got robbed. All lifters can be replaced without removing the engine. Simple remove the exhaust, intake and heads, voila. It’s a 2 man job X 4 hours X 100$ worth of lifters. Time to find a new mechanic.
On my 2024 Silverado 5.3 the transmission valve body failed at 12700 miles, while on vacation 3k miles away from home
No parts for three months
Poor quality
Poor dealer service
Worse customer satisfaction
O more gm for me
The real problem here is …China….China owns 50% of GM . Do you really think China wants GM to flourish…..I dont
BlackRock owned 125,771,387 shares of GM in April 2023, making it GM’s largest shareholder.
Vanguard owned 110,305,628 General Motors shares as of April 2023 and was the second-largest shareholder at that time.
Capital Research was GM’s third-largest shareholder as of April 2023 with 78,403,820 shares.
So enough with the misinformation.
Current info:
Top 10 institutional holdings by shares held
Name Reporting date Total holdings Position value Outstanding shares owned
Greenhaven Associates, Inc. Dec-31-2024 23.7M $1.2B 2.38%
Blackrock Inc. Sep-30-2024 104.8M $5.2B 10.53%
Vanguard Group Inc Sep-30-2024 94.4M $4.7B 9.48%
State Street Corporation Sep-30-2024 51.4M $2.5B 5.16%
Capital World Investors Sep-30-2024 48.2M $2.4B 4.85%
Harris Associates L.P. Sep-30-2024 32.4M $1.6B 3.25%
Arrowstreet Capital, Limited Partnership Sep-30-2024 30.1M $1.5B 3.03%
Franklin Resources, Inc. Sep-30-2024 28.1M $1.4B 2.82%
Geode Capital Management, LLC Sep-30-2024 23.6M $1.2B 2.37%
FMR, LLC Sep-30-2024 19.3M $953.5M 1.94%
Fund ownership details
Current quarter Previous quarter
Institutional share purchases
13.1M18.0M
Institutional shares sold
23.8M26.0M
Net institutional shares purchased
-10.8M-8.0M
Change in ownership
-2.68%-1.94%
Institutional fund & fund (no 13F Form) ownership: 39.32%
Top 10 fund holdings by shares held
Name Reporting date Total holdings Position value Outstanding shares owned
Fidelity 500 Index Fund (i) Nov-30-2024 13.9M $686.9M 1.40%
SPDR S&P 500 ETF Trust (i) Nov-30-2024 13.9M $685.3M 1.39%
iShares Core S&P 500 ETF (i) Nov-30-2024 12.7M $628.3M 1.28%
Growth Fund of America Inc (i) Nov-30-2024 11.2M $551.7M 1.12%
Washington Mutual Investors Fund (i) Oct-31-2024 25.2M $1.2B 2.53%
Putnam Large Cap Value Fund (i) Oct-31-2024 12.8M $632.2M 1.28%
Vanguard Total Stock Market Index Fund (i) Sep-30-2024 35.7M $1.8B 3.58%
Vanguard 500 Index Fund (i) Sep-30-2024 29.4M $1.5B 2.96%
Oakmark Fund (i) Sep-30-2024 13.9M $688.9M 1.40%
American Balanced Fund (i) Sep-30-2024 11.0M $544.1M 1.11%
(i) Institutional Funds
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Blackrock and vanguard both are doing the nasty in bed with China, thanks for proving his point.
William, please furnish FACTS to back up your comment. Getting “facts” off some rightwing crazy website does not equal real facts.
Facts, you liberals hate facts, it splits your head wide open!! Plus, you will just say they are false anyways…ridiculous. Thank you William!!!
so right you are
Better than making adjustments or modifications to this set-up, trade it in on a Toyota & drive problem free with higher resale value. GM won’t help you out anymore even if it’s a known defect if you’re even a little out of warranty on time or mileage. (Speaking from experience.)
Maybe you aren’t aware of over 100,000 of Toyota’s new V6 engines have been recalled for metal shavings throughout causing catastrophic failure. 100,000 may just be the tip of the iceberg.
GM will lie to you when you are in or out of warranty.
This trick has been around since the 6L80 (shift into Manual 5).
Been around since the 4l60 (shift into 3)
All GM electronic controlled transmissions (and assuming others as well) have a different shift pattern based on what gear your set in. For the 4l60 for example, shift down to 3rd engages “sport mode” where 1-2 and 2-3 shifts are delayed, and then 3rd is held with no AFM. 2nd is “snow mode” which starts in 2nd to reduce torque and leaves converter open. This changes if you engage tow-haul, and the truck assumes you are just limiting upshifts.
For the six I believe dropping into manual engages snow mode from standstill, and a downshift of 1 gear while driving and then holds it.
Not sure if other transmissions
First of all i do agree the motor itself is a very reliable motor and the ones before AFM established it as a great swap motor and some of that carried over – however the AFM is junk and with a good tune you can get the same or better mpg it offers. The lifters fail and if they haven’t in one that has over 100k its a unicorn more than the norm, and they have failed at alot less mileages in the 30-50k range. I cant comment on DFM as i would not buy a truck that new thats a GM product, being besides the AFM issues the torque converters in the 6 speeds failing has also been a problem, which again with a proper tune can be alleviated by commanding lock up differently. And the issues in newer trucks get worse, as in the 14’s where they added a thermostat that overheats the trans as well as still having the bad tuning. My perfect truck is a 07 classic sierra non AFM just in case although most of those escaped it i think with the 4l60 and i would have no worries but proper maintenance and that i would easily see 500k on the odometer.
I got a defeater device for my Camaro, and my average MPG actually went up 3 MPG
This has been covered here before. AFM retsrds the spark when going back to V8 mode, loosing power. If you jackrabbit the peddle, and your constantly switching back and forth, you’ll loose mpg. You maintain speed, you’ll greatly improve mpg. Sounds like you could get +6-7mpg by re-enabling AFM and driving more consistently.
delete the epa
Bad article, AFM is the one that was associated with some issues. You would think a GMA writer would know that.
You clearly haven’t been following engine issues for trucks and SUVs with DFM. Keep on being uninformed and criticizing those who actually know what’s going on.
I drive my Silverado in L9 and change the oil every 3000 miles.
Runs and sounds like a dream.
AFM had the issues, hence why we now have DFM. With AFM the temps in the cyl varied so much it created issues because the same 4 cyl were always shut off. With DFM, all cyl get a chance of being shut off with 17 different patterns, keeping the cyl temps more constant. But because, like everything else in life whereas the negative results get the most attn, even though they are less than 1% of the total, it gets blown out of proportion.
So what other ill effects are being enacted by driving around in ninth gear?
You may lose a little fuel economy by not shifting to 10th if you’re going fast enough, otherwise there will be no ill effects. Using the L9 allows the transition to shift through all gears up to the number chosen, so 1-9. I use this in two GM vehicles I own to disable the start-stop.
LEAVE the DFM AFM alone if you disable it the oil passages will eventually gum up because of no oil flow. The LIFTERS collapse and cause big problems. The old tale that it was bad was because the owners didn’t change there oil on time and the small passages would clog causing problems. Now we have a new problem with people who disable. These engines are complex with lots of passages and need there oil changed every 3k. We have seen just as many failures with the AFM removed as Kept. All the users who just change there oil on time every 3-4k will make there engines last to 500k but you need to change your oil!
Why don’t the GM heavy duty trucks have DFM??? Don’t they need better gas mileage? The manual transmission Camaro LT1 doesn’t have DFM. I’m just trying to figure out GM’s logic. The 2.7 TurboMax and DOHC V6 have DFM are they having issues? Technology is great when it works, I’m not sure if DFM is even required to meet the CAFE or EPA requirements.
The HD trucks are not governed by the same emissions and/or fuel economy standards as the light trucks, hence no need for AFM or DFM in them.
As for the Turbomax, it has AFM, not DFM:
https://gmauthority.com/blog/gm/gm-engines/l3b/
DFM helps on the EPA cycle, but not sure if it’s all that useful in the real world.