Are you unhappy with how the active fuel management (AFM) system reduces engine power, causing your truck to lag? While AFM helps regulate fuel consumption, it slashes your engine power by half. Additionally, it’s more likely to cause lifter failure and poor engine performance.
GM truck owners install the Range Technology AFM disabler to mitigate such issues. However, many users have reported several problems resulting from disabling the AFM system.
This guide discusses the common Range Technology AFM disabler problems and how you can resolve them. But first, let’s see how the AFM disabler works in your truck.
Question: What’s the Range Technology AFM Disabler?
AFM is a system in V6 and V8 engines that regulates fuel consumption when in a cruise situation or running in low load. It shuts off half of the V6 and V8 cylinders to ensure reduced fuel consumption. A reduction in fuel consumption comes with less engine power.
Installing the AFM disabler ensures your engine achieves maximum power or operates at total capacity. This electric device ensures your V6 or V8 engine runs with all cylinders active. It also improves engine health, saves your cylinders, and prevents lag.
Answer: Range Technology AFM Disabler Problems
Despite its benefits, the AFM disabler might pose the following problems.
- Higher engine stress
- Engine overheating
- Increased exhaust noise
- Lifter failure
- Transmission downshifting hard
- Unresponsive AFM disabler
- The engine shutting off abruptly
Higher Engine Stress
The AFM system deactivates some cylinders, thus compressing engine power. In this case, the engine doesn’t operate at its full potential, which is necessary when cruising. However, when you install the Range Technology AFM disabler, the engine works under higher pressure.
The disabler ensures that all the cylinders are active to produce maximum power. As a result, the engine is always under stress, whether in a cruising situation or low load condition.
Increased stress on your engine can trigger several issues like battery drainage, worn-out engine components, or irreparable engine damage.
The solution to this problem is turning off the disabler when the engine doesn’t require a performance boost. Stick to regular engine maintenance to ensure all parts work as they should. For instance, oil moving parts to prevent premature wear or damage.
Engine Overheating
Many issues can cause your engine to overheat. But if you notice this problem after installing the AFM disabler, it could be the leading cause.
This device adds more stress to the engine to ensure it produces more power. Therefore, the engine works harder than before to operate at its full capacity. The extra strain on the engine causes parts to overheat, which can be a big deal.
An overheated engine might damage crucial components, leading to a reduction in power. If you encounter this problem, disconnect the AFM disabler and check if the engine will overheat again. Then, activate the disabler only when the engine requires a performance boost.
Keep the engine well maintained to avoid other issues that might escalate overheating. If the engine overheats again, you must uninstall the AFM disabler.
Increased Exhaust Noise
Disabling the AFM system can cause the exhaust to emit loud noises. The thing is, when you install the Range AFM disabler, the engine works extra hard, thus emitting loud exhaust noises. This noise can intensify as you continue straining the engine and exhaust system.
Loud exhaust noises can cause noise pollution and disrupt you when driving. Moreover, it can strain and deteriorate the exhaust system over time. If left unchecked, deterioration can extend to the engine.
Like the previously discussed Range technology AFM disabler problems, avoid constantly activating this device. You can unplug it when your engine doesn’t require much power. Doing so prevents putting much strain on the engine and exhaust.
Alternatively, install a silencer to resolve the noise pollution problem. A silencer reduces exhaust noise and prevents damage to the exhaust system.
Lifter Failure
AFM lifters are more likely to fail due to general wear and tear. They are constantly working to regulate air/fuel intake into the cylinders while driving.
Installing the Range AFM disabler means the lifters remain in an open position. This fix can minimize wear and tear on lifters. Unfortunately, the AFM disabler will only delay the problem.
Many users report that the lifters fail when re-enabled after a long time. Lifters clatter when the engine shifts from V8 to V4 and can break down with time. But when back in the V8 mode, the engine works smoothly.
If lifters have completely broken down, they may fail to ensure proper air/fuel delivery to the cylinders.
To prevent this problem, re-enable the lifters once in a while. You can do this by plugging and unplugging the AFM disabler when necessary. Also, keep the lifters well-maintained by oiling them.
Then, check for early signs of wear or damage. If your lifters appear dirty or worn out, take your truck to a repair shop for an effective solution.
Transmission Downshifting Hard
Some truck owners complain that the Range Technology AFM disabler causes the transmission to downshift hard. This issue is common the first time you drive your vehicle after installing the device.
Hard downshifting occurs when slowing down or driving your truck around town. Additionally, the vehicle clunks hard when shifting from 3rd to 2nd or 2nd to 1st gears. The clunking and hard transmission shift can cause the transmission and engine to wear out faster.
Continuous driving for a few days can resolve this problem. After installing the AFM disabler, the engine can take time to adapt to the new changes. With time, it’ll start to downshift properly and make driving smoother.
If the hard downshifting persists, unplug the AFM disabler. You can also contact Range to get a new AFM disabler.
Unresponsive AFM Disabler
Sometimes, issues with the device or installation can cause the AFM disabler to be unresponsive. This is one of the AFM disabler problems that might stem from the manufacturer. If the disabler is outdated, faulty, or incompatible with your vehicle, it won’t communicate with the onboard computer.
Improper installation can trigger communication issues. As a result, the engine won’t switch from V4 to V8 mode, leading to performance problems.
To resolve this problem, check the AFM disabler to see if it’s compatible with your truck model. Also, double-check with the manual to ensure the disabler is installed correctly. A certified mechanic can also check the disabler to fix installation issues or update it.
Engine Shuts Off Abruptly
Another common problem you might encounter after installing the AFM disabler is your engine shutting off while driving. This happens abruptly and can put you at risk of an accident when driving on a highway or a hilly road.
So, how does the AFM disabler trigger this issue? When you install this electric device, it causes the engine to work under pressure. Consequently, the engine overheats, and at its peak, excessive overheating causes the engine to shut off.
Avoid stressing the engine to the peak to prevent overheating. You can do this by unplugging the AFM disabler when cruising or in a low-load condition. Then, perform regular engine maintenance to ensure all components run smoothly.

Wrapping Up
We’ve explained the seven most common Range Technology AFM disabler problems you might encounter. To fix most of these issues, unplug the disabler when your engine doesn’t require a power boost. Doing so prevents problems like higher engine stress, lifter failure, engine overheating, and high exhaust noise.
If the AFM disabler is unresponsive, check for compatibility or installation problems. The manufacturer or a professional technician can help check and fix a faulty or outdated AFM disabler. Lastly, keep up with the engine maintenance schedule to keep everything running smoothly.