General Motors’ Active Fuel Management (AFM) was introduced to make the company’s vehicles more fuel-efficient. This wasn’t just some other feature to get vehicles sold, but it had a positive impact on the environment.
What’s more, General Motors was quite early to adopt this technology compared to others. Now, while all that is commendable, one issue arose from the early adoption of the tech — reliability.
The electro-mechanical mechanism required to switch off half the engine cylinders while running is highly complex. It might be amongst the most complicated features to be added to a vehicle in general. A consequence of that and the fact that it was adopted early were reliability problems.
When this tech starts failing, it’s known to cause various problems, making the AFM something many drivers are looking to avoid. Continue reading to find out how to tell if a vehicle has Active Fuel Management and what can be done to maintain it if it does.
Article updated on 06.03.2024
What is Active Fuel Management (AFM)?
AFM, or Active Fuel Management, is a technology developed by General Motors designed to improve fuel efficiency in V6 and V8 engines.
AFM works by deactivating half of the engine’s cylinders under light load conditions, such as highway cruising, reducing fuel consumption and emissions without sacrificing performance. GM claimed that the feature improved fuel efficiency by up to 12%, but owners have reported that the figure is closer to 5% in real-world conditions.
The company believed that owners had more power than they needed most of the time. The high-capacity V8 engines were only being used to their full potential when towing or being driven in a performance-oriented manner.
During everyday driving though, it was not being used to the fullest and essentially wasting fuel. The big V6 and V8 engines didn’t need all of their cylinders while cruising on the highway and could make do with half of that.
With GM adopting this technology, it has given owners benefits that help emissions and fuel efficiency. Here are some of the benefits that you, as a driver, will enjoy:
Improved Fuel Efficiency — By reducing the number of active cylinders, AFM helps to lower fuel consumption, leading to better overall fuel economy. Under certain driving conditions, drivers can experience up to a 12% improvement in fuel efficiency.
Reduced Emissions — The engine burns less fuel with fewer active cylinders, resulting in lower carbon dioxide (CO2) emissions. This contributes to a smaller environmental footprint and helps GM vehicles comply with stricter emission standards.
Enhanced Engine Longevity —The AFM system helps reduce wear and tear on the engine by distributing the workload across all cylinders. This balanced operation can contribute to a longer engine lifespan and lower maintenance costs over time.
Optimized Performance — Despite the deactivation of cylinders, AFM ensures that the engine maintains adequate power and performance. The system is designed to provide the necessary torque and acceleration when required without compromising driving dynamics.
How does AFM work in GM vehicles?
AFM operates by selectively deactivating certain cylinders’ intake and exhaust valves, effectively turning them off when full power is unnecessary. This process is controlled by the engine control module (ECM), which monitors driving conditions and switches the cylinders on and off seamlessly to optimize fuel efficiency while maintaining the necessary power.
While the electronics were quite complex, a few additional parts were required to make it work. The only parts required were special valve lifters for the cylinder that would get deactivated and a lifter oil manifold assembly. This helped keep costs in check.
In V8 engines, Active Fuel Management switches off cylinders 1, 7, 4, and 6. In V6, the system deactivates cylinders 3 and 6. When it comes to LTA and LT2 engines, cylinder deactivation occurs on cylinders 2, 3, 5, and 8. That said, how can you tell if a vehicle has Active Fuel Management?
Identifying AFM Through Vehicle Documentation
General Motors added Active Fuel Management to several of its offerings because many of its vehicles shared the same V6 and V8 engines. Due to its advantages, GM used it widely. Here’s how to tell if a vehicle has Active Fuel Management:
Checking the Owner’s Manual
The owner’s manual is one of the primary resources for identifying whether your GM vehicle is equipped with Active Fuel Management (AFM) technology. The manual, provided by the manufacturer, contains detailed information about the vehicle’s features and specifications.
To check for AFM, look in the engine and powertrain sections. There should be a description of the AFM system, its operation, and maintenance tips. The owner’s manual will typically include diagrams and explanations to help you understand how AFM works and its benefits.
Reviewing the Window Sticker and Sales Brochure
Another way to determine if your GM vehicle has AFM is by examining the window sticker, also known as the Monroney sticker and the sales brochure. The window sticker, which is affixed to the car when it’s sold new, lists all the vehicle’s standard and optional features, including engine specifications and fuel-saving technologies like AFM. Look under the engine details or fuel efficiency sections for mentions of AFM.
Sales brochures, available at dealerships or online, also provide comprehensive details about the vehicle’s features and technologies. These brochures often highlight AFM as a key selling point for its fuel efficiency benefits. Reviewing these documents can indicate whether AFM is included in the vehicle’s specifications.
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Which Vehicles Have Active Fuel Management?
General Motors added Active Fuel Management to the following vehicles sold under the Chevrolet brand.
- Chevrolet Camaro
- Chevrolet Tahoe
- Chevrolet TrailBlazer
- Chevrolet Avalanche
- Chevrolet Silverado
- Chevrolet Suburban
- Chevrolet Impala
AFM is also found in other GM models, including several Cadillacs and many vehicles equipped with the same engines. You can check the dashboard for indicators to determine if your GM vehicle has AFM technology.
Driver Information Center (DIC)
One of the easiest ways to tell is from the driver’s seat. To determine if your V6 or V8 GM vehicle has the tech, simply look for the readout on the digital screen below the tachometer. GM called this display the Driver Information Center (DIC), and it was designed to show a bunch of helpful information, including whether the Active Fuel Management system was in operation.
Keep in mind that you might need to toggle through a few screens before you reach the one that shows the Active Fuel Management information. The display will indicate whether the engine runs as a ‘V4’ or a ‘V8’.
If you attempt to get the vehicle to switch to the V4 state, you must stay at a cruising speed below 2000 RPM. Pushing on the gas pedal a little harder will take you back into V8 mode, and when this happens, you will notice a unique sound from the exhaust.
Recognizing AFM in Your GM Vehicle’s Engine
Identifying whether your GM vehicle is equipped with Active Fuel Management (AFM) technology can help you understand its fuel-saving capabilities and ensure proper maintenance. AFM is a sophisticated system found in various GM engines, designed to enhance fuel efficiency by deactivating half of the engine’s cylinders under light load conditions.
Below, we outline the common GM engines equipped with AFM technologies and the visual indicators you can look for when checking under the hood.
Common GM Engines Equipped with AFM Technology
- 3.0 V6 LGW (Twin-Turbo)
- 3.6 V6 LGX
- 3.9 V6
- 3.9 V6 LZ8
- 4.2 V8 LTA (Twin-Turbo)
- 4.3 V6 LV3
- 5.3 V8 Vortec 5300
- 5.3 V8 LS4
- 5.3 V8 L83
- 5.3 V8 Vortec
- 6.0 V8 Vortec MAX
- 5.3 V8 Small-Block
- 6.2 V8 L99
- 6.2 V8 LT4
- 6.2 V8 LT1
- 6.2 V8 LT2
- 6.2 V8 L86
Visual Indicators of AFM When Checking Under the Hood
Specific visual cues and components under the hood can indicate the presence of AFM technology. Knowing what to look for lets you quickly identify if your vehicle is equipped with this fuel-saving system. These indicators include engine cover markings, unique solenoids, and specific valve cover designs, among others.
Engine Cover Markings — Many GM engines equipped with AFM will have a label or badge on the engine cover indicating “AFM” or “Active Fuel Management.”
Solenoids and Wiring — AFM-equipped engines have specific solenoids and additional wiring connected to the valve lifters. These solenoids control the deactivation of the cylinders and are often visible on the top of the engine.
Valve Covers — The valve covers on AFM engines may have unique shapes or additional components compared to non-AFM engines. This is due to the integration of the AFM system’s hardware.
Engine Block Casting Codes — AFM engines often have specific casting codes on the engine block. These codes can be cross-referenced with GM technical documents or online databases to confirm the presence of AFM technology.
Common DTCs on a GM Engine with AFM
Understanding the common diagnostic trouble codes (DTCs) associated with GM’s Active Fuel Management (AFM) system is crucial for diagnosing and maintaining your vehicle. While AFM technology is beneficial for fuel efficiency, it can sometimes lead to specific issues that trigger these codes.
Below, we outline the common DTCs related to AFM and the parts most likely to fail within the AFM system, helping you identify and address potential problems effectively.
List of Common DTCs Related to AFM
When malfunctioning, the AFM system in GM engines can generate several specific DTCs. These codes help pinpoint issues within the system, allowing for precise diagnostics and repairs.
P3400: Cylinder Deactivation System Bank 1
This code indicates a malfunction in the AFM system affecting the first bank of cylinders. It often points to issues with valve lifters or solenoids.
P3425: Cylinder 4 Deactivation/Intake Valve Control Circuit/Open
This code suggests a problem with the intake valve control circuit for cylinder 4, which may involve the AFM lifter or control wiring.
P3441: Cylinder 6 Deactivation/Intake Valve Control Circuit/Open
This code signals a malfunction in the AFM system related to cylinder 6, possibly due to a faulty lifter or electrical issue.
P3449: Cylinder 7 Deactivation/Intake Valve Control Circuit/Open
This code reflects a problem with cylinder 7 in the AFM system, which can be caused by a failed lifter, solenoid, or wiring issue.
P3401: Cylinder 1 Deactivation/Intake Valve Control Circuit/Open
Indicates a fault in the AFM system affecting cylinder 1, often due to problems with the lifter or the control circuit.
P3497: Cylinder Deactivation System Bank 2
This code shows an issue with the AFM system on the second bank of cylinders, possibly due to lifter failure or solenoid issues.
List of Common Engine Components That Fail on AFM
AFM technology relies on several critical components to function properly. Understanding the common parts that tend to fail can aid in troubleshooting and ensure that necessary maintenance is performed to keep the system operating smoothly.
Valve Lifters — AFM valve lifters are prone to failure due to their constant switching between active and inactive states. Common issues include collapsing or stuck lifters, which can cause misfires and DTCs.
Solenoids — The AFM solenoids control the activation and deactivation of the lifters. They can fail due to electrical issues or wear and tear, leading to malfunction codes and poor engine performance.
Oil Pressure Sensors — The AFM system requires accurate oil pressure readings to function correctly. Failed oil pressure sensors can lead to incorrect readings, affecting the system’s performance.
Wiring and Connectors — Electrical connections and wiring harnesses associated with the AFM system can become damaged or corroded, leading to intermittent faults or complete system failure.
Camshaft — The camshaft in AFM-equipped engines is specially designed to work with the deactivation system. Wear or damage to the camshaft can affect the operation of the AFM lifters, leading to performance issues and DTCs.
What maintenance is required for an AFM-equipped engine?
Regular maintenance for an AFM-equipped engine includes using the recommended engine oil type and adhering to the manufacturer’s oil change intervals, as AFM systems are sensitive to oil quality and pressure.
Frequent monitoring of oil levels is crucial to ensure the AFM system operates efficiently. Maintaining proper oil pressure is also essential, as the AFM system relies on accurate oil pressure to deactivate and reactivate cylinders.
Staying up-to-date with GM software updates is important to ensure the system functions correctly and to address any improvements or bug fixes. Promptly addressing check engine lights by diagnosing and resolving issues can prevent potential AFM-related problems and extend the engine’s lifespan.
Can the GM AFM System Be Deleted or Disabled?
As stated at the beginning, Active Fuel Management hasn’t proven to be the most reliable feature. Unfortunately, the two biggest areas of concern with vehicles equipped with the tech are noisy lifters and oil consumption.
These problems result from system inefficiencies and can be even more severe if the vehicle isn’t well-looked. This is why people consider deleting or disabling the GM AFM system altogether.
Disabling Active Fuel Management is not that complicated. All that’s required is a device called the AFM disabler. It connects to the OBDII port and does exactly what its name suggests — it disables the AFM system. The device also promises to be completely reversible and stops the engine from potentially facing the problem lifter issue.
However, if your vehicle already has lifter noise and oil consumption problems, the disabling method is too little, too late. At this stage, you will require a complete delete kit for Active Fuel Management, which includes replacing many AFM parts with standard ones.
Ensure Reliable Performance with Quality Parts from Newparts.com
Maintaining the efficiency and performance of your GM vehicle’s Active Fuel Management (AFM) system is essential for optimal fuel economy and engine longevity. Choosing a trusted supplier is crucial when sourcing reliable replacement parts for your AFM system.
Newparts.com offers a comprehensive selection of high-quality parts for GM engines equipped with AFM technology. Whether you need lifters, solenoids, oil pressure sensors, or any other component, Newparts.com ensures you receive parts that meet or exceed OEM standards.
Using top-tier components from Newparts.com, you can confidently address any AFM-related issues and maintain your vehicle’s performance and reliability. Don’t compromise on quality — visit Newparts.com today to find the right parts for your GM vehicle and keep your engine running smoothly. Shop now and experience the difference quality parts can make in your vehicle’s performance and fuel efficiency.
