How do I know if my car has Active Fuel Management?
Active Fuel Management (AFM) is GM’s cylinder-deactivation technology that can shut off cylinders to save fuel, especially during light loads. In recent years GM has largely branded this as Dynamic Fuel Management (DFM), but the function remains the same idea—adjusting how many cylinders are actively firing. To know if your vehicle has AFM or DFM, check the engine family, the dashboard indicators, and official documentation such as the window sticker or VIN lookup.
Understanding AFM and its modern evolution
AFM debuted as a fuel-saving feature on several GM V8 engines, typically deactivating four cylinders when cruising lightly. GM later expanded the concept under the Dynamic Fuel Management (DFM) umbrella, applying cylinder-deactivation logic to a wider range of engines and operating conditions. The practical effect is smoother, more efficient highway cruising, with the system automatically reactivating cylinders when you demand more power. Some older AFM systems could be disabled or modified by technicians or tuners, but newer DFM implementations are integrated into factory software and operation.
What to look for on your vehicle
To determine whether your car has AFM/DFM, use these verification methods. A quick check can save you time and help you understand your vehicle’s fuel-economy behavior.
Before we list the ways to check, note that the presence of AFM/DFM depends on model year, engine type, and trim. Below are practical, reliable steps you can take.
- Identify your engine family and year. Look under the hood or in the owner’s manual for labeling that indicates the engine family or a note about cylinder deactivation (often associated with AFM/DFM) for that specific motor.
- Check the Driver Information Center (DIC) or instrument cluster. Many GM vehicles with AFM/DFM display a message such as “AFM Active,” “Cylinder Deactivation On,” or a menu option to enable/disable the feature when the system is engaged.
- Inspect the window sticker or the vehicle’s build sheet. Some window stickers list AFM or DFM as a feature, and online VIN lookups or dealer portals can confirm its presence for your exact VIN.
- Use a VIN-based verification. A dealer or GM’s online VIN decoder can confirm whether your exact vehicle is equipped with AFM/DFM based on the production build.
- Consider an OBD-II scan. A capable scan tool may report cylinder-deactivation events or show status data related to AFM/DFM, especially when the system switches cylinders during idle or low-load driving.
Concluding paragraph: By checking the engine family, dashboard indicators, documentation, VIN, and (if needed) an OBD scan, you can confidently determine whether your GM vehicle uses AFM or its modern successor, DFM, and how it behaves during driving.
Why this matters for maintenance and driving
Knowing whether AFM/DFM is present helps set expectations for fuel economy and idle feel. If you’re considering disabling the feature for a smoother idle or different driving experience, be aware that some GM vehicles restrict or warn against disabling it, and altering the system can affect warranty or emissions compliance. If you suspect a fault with cylinder-deactivation, a dealer can perform a diagnostic update or software check to ensure the feature operates correctly.
Summary
Active Fuel Management is GM’s cylinder-deactivation technology, originally branded AFM and now commonly referred to as Dynamic Fuel Management (DFM) on newer engines. To determine whether your car has AFM/DFM, identify the engine family, look for indicators in the instrument cluster, review the window sticker or build sheet, verify via VIN, or consult a dealer or service professional. Understanding whether your vehicle uses AFM/DFM helps you manage expectations about fuel economy, idle feel, and maintenance considerations.
Which engines don't have an AFM?
The LM2 Duramax 3.0L turbo-diesel, the L8T 6.6L V8, and the LS3 have neither AFM nor the latest version, called DFM (Dynamic Fuel Management). In addition, some 5.3L V8s from 2021 and 2022 don't include either fuel-saving system due to semi-conductor shortages manufacturers were dealing with during that time.
How to identify an AFM engine?
The AFM system can be identified by its components.
- Valley Cover - The AFM cover is called the Lifter Oil Manifold Assembly (LOMA). It's ribbed with solenoids on the underside.
- Engine Block - All Gen.
- Lifters - AFM engines use special lifters for cylinders 1, 4, 6, and 7.
How to tell if a vehicle has Active Fuel Management?
And the intake. Manifold. If the um plate underneath is flat. And just got two bolts and a little drilled hole there if it's just a flat plate. Here on top of the engine in the V.
What vehicles have Active Fuel Management?
GM used the Active Fuel Management technology on a range of engines including with the GM Small Block Gen IV engine family, first-generation GM EcoTec3 engine family, second-generation GM High-Feature V6 DOHC engine family, and first-generation High-Feature V8 DOHC engine family.
