Active Fuel Management (AFM), a technology pioneered by General Motors, is engineered to boost fuel efficiency in vehicles by selectively deactivating half of the engine cylinders during light load conditions, such as highway cruising. While AFM can contribute to fuel savings, many drivers find the system’s operation, particularly the transitions between cylinder modes, to be less than ideal. If you’re seeking to maintain consistent full-cylinder operation, disabling AFM is a viable option, and one effective method is using a scan tool.
Get Amazon Exclusive Discounts
This article delves into the process of disabling AFM using a scan tool, explores the motivations behind this decision, and weighs the advantages and disadvantages of this approach. We aim to provide you with a thorough understanding to help you decide if using a scan tool to disable AFM is the right choice for your vehicle.
Understanding Active Fuel Management (AFM)
Before we discuss disabling AFM, it’s crucial to understand what it is and how it operates. AFM, also known as cylinder deactivation, is a sophisticated system designed to improve fuel economy. It works by shutting down cylinders—typically alternating cylinders on each bank in a V-engine—when the engine is not under heavy stress. For instance, when you’re maintaining speed on a flat highway, your engine requires less power. AFM detects these conditions and deactivates cylinders, effectively turning your V8 into a V4 or your V6 into a V3 temporarily.
This switch is intended to be seamless, but in practice, some drivers notice a distinct change in engine sound, feel a slight vibration, or experience a momentary hesitation as the engine transitions between modes. These transitions can be more pronounced in older AFM systems or in vehicles where the system isn’t perfectly calibrated.
Why Disable AFM?
The primary reason drivers choose to disable AFM is to eliminate the inconsistencies and sometimes jarring transitions associated with cylinder deactivation. Here are a few common motivations:
- Eliminate Engine Hesitation or Jerking: The most frequently cited reason is the noticeable shudder or hesitation when the AFM system engages or disengages. This can be particularly bothersome in stop-and-go traffic or during gentle acceleration.
- Restore Consistent Engine Sound: Many enthusiasts prefer the constant rumble of a full V8 or V6 engine. AFM can alter the exhaust note, sometimes producing a less satisfying sound when running on fewer cylinders.
- Performance Preference: Some drivers believe that running on all cylinders at all times provides more predictable and responsive power delivery, especially during quick acceleration.
- Preemptive Maintenance Concerns: Although AFM is generally reliable, some worry about the long-term effects of repeatedly switching cylinders on and off, fearing uneven wear or potential component failures in the AFM system itself.
While modern AFM systems are refined, these concerns are valid for some drivers, leading them to seek methods to disable the system.
Disabling AFM with a Scan Tool: A Step-by-Step Guide
A scan tool, or OBD-II (On-Board Diagnostics II) tool, is an indispensable device for modern vehicle maintenance. It connects to your car’s computer system, allowing you to read diagnostic codes and, in more advanced tools, modify vehicle settings. Disabling AFM is one such modification possible with the right scan tool.
Here’s how to disable AFM using a scan tool:
-
Select a Compatible Scan Tool: Not all scan tools offer the capability to modify engine control module (ECM) settings. You’ll need a tool that specifically supports advanced functions like parameter adjustments or ECU reprogramming. Popular choices known for AFM disablement capabilities include:
- HP Tuners: Widely favored by tuning professionals, offering extensive control over engine parameters.
- Diablosport Tuners: Known for user-friendliness and pre-loaded tunes, with options to customize settings like AFM.
- EFI Live: Another professional-grade tool providing deep access to engine and transmission control systems.
- Autel Scanners: Certain high-end Autel models offer advanced functions including ECU coding and adaptations which may include AFM control.
Ensure the scan tool you choose is compatible with your vehicle’s make, model, and year.
-
Establish Connection: Locate the OBD-II port in your vehicle. It’s typically situated under the dashboard on the driver’s side. Turn your vehicle’s ignition to the “ON” position (engine off) and plug the scan tool securely into the OBD-II port.
-
Navigate to AFM Settings: Power on the scan tool and navigate through its menu system. The exact steps will vary depending on the tool’s interface, but generally, you’ll need to enter the vehicle’s diagnostic or tuning section. Look for options related to:
- Engine Control Module (ECM)
- Powertrain Control Module (PCM)
- Fuel System Settings
- Cylinder Deactivation
- Active Fuel Management
Refer to your scan tool’s user manual for precise navigation instructions.
-
Disable AFM: Once you locate the AFM settings, the tool should present an option to disable or deactivate the system. This might be a simple toggle switch or a setting you need to change from “Enabled” to “Disabled” or “Off”. Select the option to disable AFM.
-
Save and Apply Changes: After disabling AFM, you must save the new settings. The scan tool will typically prompt you to confirm your changes and may require you to cycle the ignition (turn the car off and then back on) for the new settings to take effect. Follow the on-screen prompts carefully to ensure the changes are correctly saved and applied to your vehicle’s ECM.
-
Verify AFM Disablement: After completing the process, start your vehicle and drive under conditions where AFM would normally engage (light throttle, steady cruising). Observe if the engine now operates consistently without transitioning to cylinder deactivation mode. You might notice a slightly different engine sound or feel smoother power delivery.
OBD-II port commonly located under the dashboard, used for connecting scan tools to disable AFM.
Advantages of Using a Scan Tool to Disable AFM
Opting for a scan tool to disable AFM offers several benefits:
- Comprehensive Vehicle Control: Scan tools provide access to a wide array of vehicle parameters beyond just AFM. You can often adjust other engine and transmission settings, read diagnostic trouble codes, and perform various maintenance procedures. This makes a scan tool a versatile investment for vehicle owners interested in diagnostics and customization.
- Reversibility: Disabling AFM via a scan tool is typically reversible. If you decide to re-enable AFM in the future, you can simply use the scan tool to revert the setting back to its original “Enabled” state.
- No Additional Hardware: Unlike plug-in AFM disabler devices, using a scan tool doesn’t require any permanent hardware installation. Once you’ve made the change, the scan tool can be disconnected and stored until needed again.
- Customization Potential: For users already interested in vehicle tuning or performance modifications, a scan tool opens up possibilities for further customization beyond just AFM, such as adjusting throttle response, shift points, and more (depending on the tool’s capabilities and vehicle support).
Potential Drawbacks of Using a Scan Tool to Disable AFM
While effective, using a scan tool to disable AFM also has potential downsides:
- Initial Investment: Capable scan tools that allow ECM modifications can be expensive. Professional-grade tools like HP Tuners or Diablosport can range from several hundred to over a thousand dollars. This cost might be prohibitive if your sole purpose is to disable AFM.
- Learning Curve: Operating a scan tool and navigating its software interface requires some technical aptitude. While many tools are designed to be user-friendly, understanding the menus and options related to vehicle systems can be daunting for beginners.
- Warranty Implications: Modifying ECM settings can potentially void your vehicle’s powertrain warranty. Manufacturers may argue that altering factory settings could negatively impact vehicle reliability or emissions compliance. Always review your warranty terms and conditions before making such modifications.
- Risk of Incorrect Settings: Improper use of a scan tool or making incorrect changes to vehicle settings can lead to performance issues or even damage to vehicle systems. It’s crucial to follow instructions carefully and, if unsure, seek guidance from experienced users or professionals.
- Fuel Economy Reduction: Disabling AFM will likely result in a decrease in fuel economy, especially during highway driving. AFM is designed to save fuel, and by disabling it, your engine will always operate at full cylinder capacity, consuming more fuel under light load conditions.
Alternative: AFM Disabler Devices
For those seeking a simpler, more plug-and-play solution, AFM disabler devices are available. These devices typically plug into your vehicle’s OBD-II port and electronically signal the system to keep AFM disengaged without requiring software modifications.
Pros of AFM Disablers:
- Ease of Use: Simple plug-and-play installation.
- Lower Cost: Generally less expensive than advanced scan tools.
- Easy Removal: Can be quickly removed to re-enable AFM or for warranty concerns.
Cons of AFM Disablers:
- Limited Functionality: Only designed to disable AFM, lacking the broader diagnostic and customization capabilities of a scan tool.
- Potential for OBD-II Port Conflict: Some devices may interfere with other OBD-II port functions or devices.
- Still May Affect Warranty: While less traceable than ECM reprogramming, some dealerships might still flag the use of aftermarket OBD-II devices.
Which Method is Right for You?
The choice between using a scan tool and an AFM disabler depends on your technical comfort, budget, and long-term vehicle maintenance goals.
- Choose a Scan Tool if: You are comfortable with automotive technology, interested in broader vehicle diagnostics and potential tuning, and want reversible and comprehensive control over vehicle settings beyond just AFM.
- Choose an AFM Disabler if: You seek a straightforward, cost-effective, and easily reversible solution specifically for disabling AFM, and do not require the advanced functionalities of a scan tool.
Conclusion
Disabling AFM can significantly alter your driving experience by providing consistent engine performance and eliminating unwanted transitions. Using a scan tool offers a robust and versatile method to achieve this, along with broader vehicle control capabilities. However, it’s essential to weigh the initial cost, learning curve, potential warranty implications, and fuel economy trade-offs. Whether you opt for a scan tool or a simpler AFM disabler, understanding the pros and cons will ensure you make an informed decision that best suits your needs and preferences for your vehicle. Always prioritize safety and consult with automotive professionals if you have any doubts or concerns about modifying your vehicle’s systems.
