How to Disable AFM on 5.3?

Active Fuel Management (AFM) is a system in some 5.3L GM truck engines that disables cylinders to improve fuel economy. Many owners want to disable AFM to regain lost power and prevent lifter failure. Here are the main ways to turn off AFM on a 5.3 motor.

Checking if Your Vehicle Has AFM

The first step is confirming if your 5.3L engine has AFM from the factory. Easy ways to check include:

• Check if there is an “AFM” badge on the engine cover
• Look for displacement on demand (DOD) references in manuals
• Scan for P3000, P3006, P0520-P0523, and P2138 AFM codes

If you have AFM codes set, your 5.3L most likely has the system.

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Downsides of AFM

There are some drawbacks to having AFM activated from the factory:

Lost Power and Performance

AFM robs 20% of the engine’s power and torque when cylinders deactivate. This hurts towing performance and acceleration. Disabling AFM restores full-time 8 cylinder muscle.

Hardware Methods to Disable AFM

One route is using hardware devices to turn off AFM operation:

AFM Disabler Devices

Aftermarket modules plug into the OBD2 port and send disable commands to the PCM to turn off AFM triggering maps. This keeps all cylinders activated.

Range Technology Module

The Range AFM disabler box plugs inline with oil pressure sensor to send fixed 3-bar signal that keeps cylinders firing. This method is $100 and easy to install.

AFM Delete Plates

These metal plates block oil pressure from lifters to prevent cylinder deactivation sequences. Simple DIY install but doesn’t address tuning issues.

Tuners to Disable AFM

Custom PCM tuning with handheld flash tools or custom tuners can disable AFM in software:

Custom Tuning

Professional dyno custom tunes can optimize spark and fuel parameters for best performance with AFM off. This addresses tuning flaws but costs $400+

Software Methods to Disable AFM

For DIYers, scanner software tools allow disabling AFM yourself:

Scanning Tools to Disable AFM

Software like HP Tuners and EFILive allow reprogramming the PCM to turn off DOD activation based on RPM, load, etc limits you set.

HP Tuners Software

HP Tuners credits let you tune AFM triggering maps yourself for $500. There is a learning curve but works great when mastered.

EFILive Tuning Software

EFILive has custom operating system to disable AFM in the PCM tuning. It costs $650 but makes disabling cylinders easy.

OBD2 Programming Tools

Cheap OBD tools like Bully Dog and Range flash tune files that disable AFM are loaded to the truck’s PCM through the port. These cost under $150 but offer less custom tuning ability.

Conclusion

Most Reliable Method to Disable AFM

For most 5.3L Silverado owners, the Range AFM disabler module is the simplest plug and play device to turn off cylinder deactivation reliably. It costs less than $100 and takes 10 minutes to wire up underneath the hood.

This module taps into the PCM’s oil pressure sensor circuit to fix the variable 3-bar signal for max power. If you also want to address any tuning issues, a custom performance shop dyno tune with AFM disabled optimizes all parameters.

FAQs

Does disabling AFM really increase horsepower and mpg?
Yes, expect 30-50 extra horsepower and 2-3 mpg from killing cylinder deactivation.

Is disabling AFM bad or hard on the engine?
No, it allows constant stable combustion versus variable cyclinder events with AFM on.

Will disabling AFM void my powertrain warranty?
No, aftermarket AFM deletion itself does not void factory GM warranty coverage.

Can I revert back to factory AFM enabled later if desired?
Yes, AFM disabling modules can be unplugged to revert back to stock if needed.

Does turning off AFM require a new PCM or flashing ECU?
No hardware changes needed – all methods alter AFM maps in existing PCM.