If you’re the proud owner of a modern vehicle, you may have heard the term “active fuel management” thrown around. But what exactly is it, and how do you know if your car has it?
Active fuel management, also known as cylinder deactivation, is a system that helps improve a vehicle’s fuel efficiency by shutting down some of the engine’s cylinders when they’re not needed. This can save you money at the gas pump, but it can be challenging to tell whether your vehicle has this feature.
In this blog, I will explore signs that your car has active fuel management and what it means for your driving experience. So buckle up and get ready to learn more about this innovative technology!
- Improved Engine Efficiency and Performance:
Active fuel management can improve engine efficiency and performance by allowing the engine to operate in V4 mode during low-load and cruising situations.
By running on fewer cylinders, the engine consumes less fuel and produces fewer emissions, which can result in improved efficiency and performance.
When the engine needs more power, the AFM system seamlessly switches to V8 mode, providing the necessary power and torque.
This can improve acceleration, towing capacity, and overall engine performance.
- Best Suited for Certain Applications or Engine Designs:
AFM can best suit specific applications or engine designs, such as large displacement V8 engines commonly used in pickup trucks and SUVs.
These engines tend to have low fuel economy ratings, and AFM can help improve their efficiency without sacrificing power or performance.
AFM can also be helpful in smaller engines used in passenger cars or light-duty trucks, where the technology can help achieve fuel efficiency without sacrificing performance.
- Reduces Fuel Consumption in Low-Load and Cruise Situations:
AFM can reduce fuel consumption in low-load and cruise situations, where the engine runs at lower RPMs and does not require as much power.
This can improve fuel economy, reduce emissions, and lower operating costs.
- Can Interfere with Normal Engine Operation:
Active fuel management can interfere with regular engine operation, as the system relies on complex electronics and mechanical components to switch between V4 and V8 modes.
If any of these components fail, it can cause the engine to run poorly.
Additionally, some drivers may notice a slight delay or hesitation when the system switches between modes, impacting the overall driving experience.
- Leading to Decreased Performance and Reduced Overall Durability:
Some experts have suggested that active fuel management can lead to decreased performance and reduced overall durability of the engine.
This is because the system can stress more on specific components, such as the camshaft and lifters, which can wear out quickly over time.
Additionally, some drivers have reported issues with oil consumption and engine knock, which the AFM system can cause.
- May Not Be as Effective at Improving Engine Efficiency as Other Strategies:
While active fuel management can improve engine efficiency in certain driving conditions, it may not be as effective as other strategies, such as direct injection or turbocharging.
These technologies can provide more significant gains in efficiency and performance without the added complexity and maintenance requirements of active fuel management.
You can determine whether your vehicle has active fuel management in several ways. Here are some of the most common signs to look out for:
- Valley Cover
If you look at your vehicle’s engine block and see a valley cover, that indicates that your car has active fuel management.
This cover is located between the cylinder heads and covers the lifter valley.
- AFM Towers
Another clue that your vehicle has active fuel management is the presence of AFM towers on the engine block.
These small towers can be seen on the top of the engine block and hold the lifters in place.
- Special Oil Lifters
Active fuel management requires special oil lifters to operate appropriately.
If you have these lifters in your engine, it’s a good sign that your vehicle has this feature.
- Valley Cover Gasket
Besides the valley covers itself, the gasket that seals it may indicate whether your vehicle has active fuel management.
Look for a gasket with a distinctive shape or design, as this may be a sign that it’s designed for an engine with active fuel management.
- Lifter Guides
Active fuel management also requires unique lifter guides to keep everything working smoothly.
These guides can typically be seen inside the engine block.
- Special Camshaft
The camshaft in an engine with active fuel management is typically designed to work specifically with this feature.
Look for a unique camshaft, which may indicate that it’s designed for an engine with active fuel management.
- Powerful Fuel Pump
Active fuel management requires a powerful fuel pump to maintain the necessary pressure in the engine.
If your fuel pump is potent, this may be a sign that your vehicle has this feature.
- V8/V4 Icon
Finally, some vehicles with active fuel management may have a V8/V4 icon on the dashboard or in the instrument cluster.
This indicates that the engine can run on eight or four cylinders, depending on the driving conditions.
|Engine Family||Engine Name/Model|
|GM Small Block Gen IV engine family||5.3L V-8 Vortec 5300|
|GM Small Block Gen IV engine family||3.9L V-6 LZ8|
|GM Small Block Gen IV engine family||5.3L V-8 LS4|
|GM Small Block Gen IV engine family||6.2L V-8 L99|
|First-generation GM EcoTec3 engine family||4.3L V-6 LV3/td|
|First-generation GM EcoTec3 engine family||5.3L V-8 L83|
|First-generation GM EcoTec3 engine family||6.2L V-8 L86|
|Second-generation GM High-Feature V6 DOHC engine family||3.6L V-6 LGX Naturally Aspirated|
|Second-generation GM High-Feature V6 DOHC engine family||3.0L V-6 LGW Twin-Turbo|
|First-generation High-Feature V8 DOHC engine family||4.2L V-8 LTA Twin-Turbo|
Which Vehicles Have Active Fuel Management?
|Chevrolet Silverado||5.3L V-8 Vortec 5300|
|Chevrolet Tahoe||5.3L V-8 Vortec 5300|
|Chevrolet Suburban||5.3L V-8 Vortec 5300|
|GMC Sierra||5.3L V-8 Vortec 5300|
|GMC Yukon||5.3L V-8 Vortec 5300|
|Cadillac Escalade||6.2L V-8 L99|
|Chevrolet Impala||3.9L V-6 LZ8|
|Chevrolet Monte Carlo||5.3L V-8 LS4|
|Buick LaCrosse||3.6L V-6 LFX|
|Cadillac DTS||4.6L V-8 Northstar LD8|
|Cadillac STS||4.4L V-8 Northstar L47|
|Cadillac XLR||4.6L V-8 Northstar L37|
|Cadillac XTS||3.6L V-6 LFX|
|Chevrolet Avalanche||5.3L V-8 Vortec 5300|
|Chevrolet Colorado||3.6L V-6 LFX|
|GMC Canyon||3.6L V-6 LFX|
|GMC Envoy||5.3L V-8 Vortec 5300|
|Pontiac Grand Prix||5.3L V-8 LS4|
- Problem 1: Higher Maintenance Costs
AFM can cause higher maintenance costs, leading to excessive oil consumption, lifter failure, and camshaft wear.
These issues can result in costly repairs and maintenance for the vehicle owner.
- Problem 2: Towing Capacity
AFM can cause reduced vehicle towing capacity because it deactivates some of the engine’s cylinders to save fuel, reducing the engine’s power output.
When the engine is working in V4 mode, it produces less power than when it is working in V8 mode, which can affect the vehicle’s ability to tow heavy loads.
Additionally, AFM causes issues such as lifter failure and camshaft wear, further reducing the engine’s power output and towing capacity.
- Problem 3: Increased Engine Noise
AFM can cause increased engine noise in some cases.
When the engine switches from V8 to V4 mode, it can cause a change in the engine’s sound, which some drivers may perceive as increased engine noise.
Even a malfunctioning lifter, malfunctioning engine control module and even low oil pressur can cause the engine to create noises.
Additionally, AFM can cause issues such as engine knocking or pinging, contributing to increased engine noise.
- Problem 4: Compatibility Issues
Not all engines are compatible with AFM, and retrofitting an engine with AFM can be expensive and complicated.
- Inspect the oil pressure: Oil pressure difficulties may be brought on by AFM.
An oil pressure gauge can be used to check the oil pressure. Low oil pressure could be an indication of blocked oil travel or an issue with the oil pump.
A professional can check the oil passageways and oil pump for problems and make any necessary repairs.
- Check the engine control module (ECM): The AFM system is managed by the ECM.
Increased engine noise may be a sign that the ECM isn’t working properly.
The ECM can be examined by a mechanic who can then fix any problems using a diagnostic device.
- Inspect the camshaft: Camshaft difficulties may be brought on by AFM. Look for wear and damage on the camshaft.
It can be necessary to replace the camshaft if it is worn out or damaged.
Yes, it is possible to deactivate Active Fuel Management (AFM) system. There are several methods to disable the AFM system:
- Disconnecting the brake booster vacuum sensor is the simplest method of deactivating AFM.
By disconnecting the brake booster vacuum sensor, the system will not be able to activate and will remain deactivated.
However, this method may trigger a check engine light and could impact other systems in the vehicle.
- Using a tuner or programmer to disable the system. Some tuners and programmers can disable AFM in the vehicle’s engine control module (ECM).
This method is more involved than disconnecting the brake booster vacuum sensor, but it is a more comprehensive way to deactivate the system without triggering any error codes.
- Installing an AFM delete kit is the most involved method of deactivating AFM.
An AFM delete kit typically involves replacing the camshaft and lifters in the engine with non-AFM components.
This method is more expensive and time-consuming than the other two methods but is the most effective way to remove the AFM system from the engine.
However, it is essential to note that disabling the AFM system may affect the vehicle’s fuel economy and performance.
The AFM system was designed to increase fuel economy without reducing the engine’s performance.
Additionally, deactivating the AFM system may cause damage to the engine if not done correctly.
The main difference between AFM and DFM is that AFM turns off half of the engine’s cylinders under light-load conditions.
While DFM can turn off any number of cylinders, from one to seven, depending on the driving conditions.
AFM detects when the engine does not need full power and will stop fuel delivery to half the cylinders, 3 on a V6 engine and 4 on a V8 engine.
While AFM would shut off the same cylinders every time the system would activate, with DFM, the system can turn off different cylinders each time, depending on the driving conditions.
No, Honda cars do not have Active Fuel Management (AFM) technology.
AFM is a trademarked name for the automobile variable displacement technology from General Motors.
Active Fuel Management (AFM) kicks in during driving situations, such as highway cruising when the engine does not need full power.
AFM allows a V6 or V8 engine to “turn off” half of the cylinders under light-load conditions to improve fuel economy.
The AFM activation and deactivation are controlled by the Valve Lifter Oil Manifold or VLOM, which consists of four electronically operated solenoids.
The AFM system was designed to increase fuel economy by allowing half of the engine’s cylinders to be used during freeway driving.
The cost to repair the Active Fuel Management (AFM) system can vary depending on the specific issue and the vehicle model.
For example, the AFM Lifter Replacement Kit for GM 5.3 costs $599.99, while the 2007 – 2014 Active Fuel Management Kit costs $1,202.87.
However, it is essential to note that some shops may recommend replacing the entire engine, which can be more expensive.
Some local shops offer AFM removal at no extra charge.
It is recommended to consult with a trusted mechanic to determine the specific issue and repair cost for the AFM system.
Dynamic Fuel Management (DFM) is a General Motors engine technology that automatically and seamlessly manages power and fuel efficiency by being strategic about what engine cylinders are used.
DFM is also known as Dynamic Skip Fire. The DFM system allows the engine to turn off cylinders when driving in situations that don’t require full power, like cruising on the freeway.
DFM and Active Fuel Management (AFM) are engine systems that GM has implemented for better fuel efficiency without sacrificing performance.
Active Fuel Management (AFM) can save up to 8% of fuel during highway cruising by deactivating some of the engine’s cylinders when not needed.
However, the fuel savings are sometimes less than expected, and in some cases, AFM can even cause an increase in fuel consumption.
The amount of fuel savings between V-8 and V-4 modes is a gray area because of all the variables involved. Nonetheless, AFM is a fuel-saving technology that can improve fuel efficiency and reduce fuel costs for vehicle owners.