8 things every GM truck owner should know about Active and Dynamic Fuel Management, and how a plug-in disabler keeps every cylinder firing.
The short answer
An AFM/DFM disabler is a small module that plugs into your GM truck's OBD-II port and keeps the engine running on all cylinders. That stops Active Fuel Management (AFM) or Dynamic Fuel Management (DFM) from shutting cylinders off, which takes the constant switching stress off the lifters.
Active Fuel Management (AFM) is on many GM V6 and V8 trucks, SUVs and cars from about 2007 to 2018. Dynamic Fuel Management (DFM) replaced it on many 2019 and newer trucks.
Both do the same basic thing: when you're cruising with light throttle, the engine shuts off some of its cylinders to save a little fuel, then turns them back on when you need power.
AFM runs your V8 as a V4. DFM can switch between even more cylinder combinations.
Cylinders are shut off by special lifters that collapse on command and lock back up when the cylinder comes back. On a normal drive they cycle on and off over and over.
When one of those lifters sticks, you can get a tick, a misfire and, in bad cases, a chewed-up camshaft with metal sent through the engine.
Lifter and cam repairs commonly run several thousand dollars.
An AFM/DFM disabler is a small module that plugs into your truck's OBD-II port. It keeps the engine in full-cylinder mode, so AFM or DFM never kicks in.
No switching means the lifters aren't constantly collapsing and re-locking every time you ease off the gas.
The OBD-II port is the 16-pin plug under the dash on the driver's side, usually just above the pedals. Push the disabler in, start the truck, and you're done.
No tools, no wiring, no app and no shop visit.
Unplug it anytime and your truck goes right back to stock.
A tune rewrites your engine computer. A plug-in disabler doesn't, so there's nothing to undo. Pull it out and the truck runs exactly like it did from the factory.
Under the Magnuson-Moss Warranty Act, a manufacturer can't void your whole warranty just because you used an aftermarket part. It's still smart to unplug it before a dealer visit.
No more shudder around cruising speed when cylinders drop out, and no lag when you step on it and they wake back up. It's most noticeable in stop-and-go traffic, on hills and when towing.
Many owners also report using less oil between changes, since AFM can pull oil past the piston rings while cylinders are shut off.
Fuel economy: expect a small drop, usually around 0.5 to 1 mpg on the highway.
Existing damage: a disabler can't fix a lifter that's already failing. If your engine is ticking or misfiring, get it diagnosed first.
Parking: if the truck will sit for more than a week, unplug it, same as any OBD-II plug-in.
Inspection: emissions and inspection rules vary by state, so check yours.
A tune or a lifter delete kit also stops AFM. But a tune changes your engine computer, and a delete kit means tearing the engine apart at a shop. A plug-in disabler gets you the same full-cylinder operation for under $100, and it's fully reversible.
| Feature | RevGuard | AFM delete (shop) | Doing nothing |
|---|---|---|---|
| Protects engine | |||
| Smoother driving | |||
| Less oil burn | |||
| Quick installation | |||
| Fully reversible | |||
| No ECU reflash | |||
| Under $100 |
Compatibility checker
Pick your make, model and year. We'll tell you right away if RevGuard works with your truck.
Not sure about your vehicle? Email support@revguardauto.com and we'll confirm for free. Every order is covered by our 30-day money-back guarantee.
RevGuard™ AFM/DFM Disabler
$89.00$178.00
No. GM V6 and V8 engines ran on every cylinder for decades before AFM existed, and non-AFM versions of these engines still do. AFM was added to meet fuel economy targets, not to protect the engine.
A plug-in disabler doesn't modify your engine computer, and under the Magnuson-Moss Warranty Act a manufacturer can't void your whole warranty just because you used an aftermarket part. We still recommend unplugging it before any dealer service visit.
Yes, on supported model years. AFM and DFM work on the same principle and use the same kind of collapsing lifters. Some 2019 and newer trucks with the 10-speed transmission need a quick check, so use the compatibility checker above or email us your VIN.
The disabler is designed to keep the engine in full-cylinder mode without setting diagnostic codes, so your dash should look the same as it does now. If you ever see a new light after installing it, unplug it and contact us.
It draws very little power when the truck is off. If the vehicle will sit for more than a week, pull it out, same as any OBD-II plug-in.
No. A disabler takes the switching stress off healthy lifters to help prevent future damage. It can't repair a lifter or camshaft that's already damaged, so get a ticking or misfiring engine diagnosed first.
Ten seconds under the dash. Try it for 30 days, and if you're not happy, get your money back.
Shop the AFM/DFM Disabler · $89