If you drive a refreshed 2022.5 or newer Silverado or Sierra, or a 2021 or newer Tahoe, Suburban or Yukon with the V8, your engine is running GM’s most aggressive cylinder deactivation system yet. Owners call these “the 10 speed trucks,” and for years most AFM and DFM disablers were not built for them. This guide covers what DFM actually does, the numbers behind it, exactly which models are covered, and how to switch it off.
Short answer: the FullForce 10 Speed plugs into the OBD2 port in under 2 minutes, keeps DFM (GM’s newer AFM) off so the V8 stays on all 8 cylinders, and turns auto start stop off every time you start the truck. It fits the 5.3L and 6.2L V8 in six vehicles, listed below.
What Dynamic Fuel Management is
GM introduced Dynamic Fuel Management (DFM) on the 2019 Silverado 1500 and Sierra 1500 with the 5.3L L84 and 6.2L L87 V8s. It replaced Active Fuel Management (AFM), which could only switch between 8 cylinders and 4.
DFM can shut off cylinders in 17 different patterns, anywhere from 2 to 8 cylinders firing. Its controller watches the throttle and decides how many cylinders to run about 80 times per second. In GM’s own testing, a 2019 Silverado with the L84 spent more than 60 percent of an industry standard drive cycle on fewer than eight cylinders, about 9 percent more than a comparable 2018 truck with AFM.
That is great for the window sticker. It also means the parts doing the switching work far harder.
Why owners turn DFM off
To shut a cylinder off, its lifters collapse on command using a small spring loaded locking pin that is controlled by oil pressure. Every time DFM switches, that pin releases and locks again. On a normal commute that can happen hundreds of times.
That pin is a known wear point. When it wears, the lifter can stick or collapse. It usually starts as a tick at idle, then a misfire, and it can end with a damaged camshaft. Repair quotes for lifters and a cam commonly run $4,000 to $8,000. Regular oil changes help an engine in many ways, but they do not stop the switching, because the switching is how DFM is designed to work.
Keeping DFM off locks the engine on all 8 cylinders, so the deactivation lifters are never told to switch and the pins stop cycling.
Exactly which 10 speed trucks are covered
| Vehicle | Model years | Engines |
|---|---|---|
| Chevrolet Silverado 1500 | 2022.5 to 2026 | 5.3L V8 (L84), 6.2L V8 (L87) |
| GMC Sierra 1500 | 2022.5 to 2026 | 5.3L V8 (L84), 6.2L V8 (L87) |
| Chevrolet Tahoe | 2021 to 2024 | 5.3L V8, 6.2L V8 |
| Chevrolet Suburban | 2021 to 2024 | 5.3L V8, 6.2L V8 |
| GMC Yukon | 2021 to 2024 | 5.3L V8, 6.2L V8 |
| GMC Yukon XL | 2021 to 2024 | 5.3L V8, 6.2L V8 |
What “2022.5” means: GM refreshed the Silverado and Sierra 1500 partway through the 2022 model year, with a new front end and a new interior that has a large horizontal center touchscreen. The 10 Speed fits the refreshed trucks. The 2022 “Limited” trucks built on the older body, and 2021 and older trucks, use the original FullForce V8 & V6 disabler instead.
Not covered: the 2.7L TurboMax, the 3.0L Duramax diesel, the Cadillac Escalade, and 2025 or 2026 Tahoe, Suburban and Yukon.
Check for YK9 first. During the chip shortage GM built some 5.3L trucks from about March 2021 through the end of the 2022 model year without DFM or auto start stop. They carry RPO code YK9 on the glovebox label. If yours has it, there is no DFM to turn off. The 6.2L was not affected.
Not sure? The fitment checker on the product page will confirm your exact model, year and engine in a few seconds.
Your options for turning DFM off
| Method | How it works | Trade off |
|---|---|---|
| Manual / L mode or Tow/Haul | Keeps DFM from engaging while selected | You have to remember it every single drive |
| Tune or reflash | Rewrites the factory calibration | Changes the factory software; harder to undo |
| Inline module at the computer | Wires in at the engine computer | Install means unplugging connectors at the ECM |
| FullForce 10 Speed | Plugs into the OBD2 port and keeps DFM off | Small fuel trade off when cruising |
How the FullForce 10 Speed works
The module plugs into the OBD2 port under the driver’s side dash. It overrides the computer’s cylinder deactivation command, so the engine stays locked in full 8 cylinder mode. At the same time it turns auto start stop off every time you start the truck, which is the same as pressing the button, done for you on every drive.
It is the only 10 speed disabler that shuts off DFM and auto start stop from a single OBD2 plug. No splicing, no wiring at the computer, nothing to reprogram.
Install in four steps
- Find the port. It is the rectangular OBD2 port under the dash on the driver’s side.
- Plug it in. No tools, no dash or radio removal. Under 2 minutes.
- Start the truck. DFM and auto start stop turn off on their own.
- Drive. All 8 cylinders, every drive, and no more engine shutdowns at red lights.
What it is not
- Not a tune. The factory computer software is left untouched.
- Not a delete. No parts are removed.
- Not permanent. Unplug it and the truck is back to stock.
- Not a repair. It helps prevent future DFM wear. It does not undo damage that has already happened.
The honest trade off
Cylinder deactivation exists to save a little fuel at light cruise. With DFM off you give up that small saving. In exchange the engine runs on all 8 cylinders all the time, the lifters stop cycling, and the truck stops shuffling between cylinder patterns under your foot. Most owners who tow, haul or keep their trucks for the long haul are happy with that trade.
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Frequently asked questions
Will a DFM disabler fit my 2023 Silverado?
Yes, if it has the 5.3L or 6.2L V8. The FullForce 10 Speed fits the refreshed 2022.5 to 2026 Silverado 1500 and Sierra 1500 with the 5.3L (L84) or 6.2L (L87). It does not fit the 2.7L TurboMax or the 3.0L Duramax diesel.
Does it work on a 2021 Tahoe, Suburban or Yukon?
Yes. The 2021 to 2024 Tahoe, Suburban, Yukon and Yukon XL with the 5.3L or 6.2L V8 are covered. The 2025 and 2026 SUVs and the Cadillac Escalade are not on the list yet.
My truck is a 2021 Silverado or a 2022 Limited. Which one do I need?
Those trucks use the older body style, so they take the original FullForce V8 & V6 disabler, not the 10 Speed.
Does it tune or reprogram my truck?
No. It works through the OBD2 port and does not tune, flash or reprogram the factory computer. Unplug it and the truck goes straight back to stock behavior.
Will it fix a lifter that is already ticking?
No. It helps prevent future DFM wear by stopping the cycling. It does not undo damage that has already happened. If you already hear a tick or feel a misfire, have the engine inspected first.
Does it also turn off auto start stop?
Yes. It turns auto start stop off automatically every time you start the truck, so you no longer have to press the button on every drive.
Related reading: AFM vs DFM explained · How to turn off auto start stop permanently · AFM disabler compatibility list
Sources and further reading
GM Dynamic Fuel Management, Green Car Journal
GM Dynamic Fuel Management cylinder deactivation, GM Authority
Understanding GM’s Active and Dynamic Fuel Management, Tomorrow’s Technician
GM AFM vs DFM, Underhood Service
GM AFM and DFM comparison, Engine Professional
