What is AFM?
AFM stands for Active Fuel Management, and is also referred to as Displacement on Demand. This was offered in 2007-2018 GM applications such as Silverado, Sierra, Camaro, Corvette, and more. AFM/DOD refers to the shutting off of four cylinders for alleged better fuel economy.
What is DFM?
DFM stands for Dynamic Fuel Management, and is also referred to as Dynamic Skip Fire. Basically, it is a more advanced version of AFM/DOD found in the 2019 & up GM vehicles. Instead of only shutting off the same four cylinders each time, DFM is more sophisticated, controlling all cylinders in different patterns based on the needs of the driver.
What is the problem with these systems?
Virtually all AFM and DFM systems will have failed lifters eventually. It is a very problematic system. A failure can start as a misfire, and may or may not come with the audible lifter tick. If one continues to drive on a failing lifter, it can come apart catastrophically, sending metal throughout the engine or even becoming stuck in the bore. It is important to stop driving and diagnose immediately when you start to hear noise or feel a misfire.
What is the solution?
The best solution for a failing AFM or DFM system is to remove it entirely, replacing it with normal, non-collapsing lifters. The cam must be replaced also to a non-DOD/AFM style cam. Factory DOD/AFM camshafts have slightly shorter lobes on the DOD/AFM cylinders, so if the lifters are replaced but the cam is not, you will have a misfire on those cylinders.
It does not generally make sense to replace with new AFM/DFM components, as the same problem is bound to happen again down the road.
Some people take the opportunity to swap in an aftermarket cam for more performance, although there are factory non-DOD cams for those who only want to fix the problem and not modify their vehicle.
What kind of tuning can be done for AFM/DFM?
It is possible to disable AFM/DFM in the ECM. This MUST be done if you are physically removing these components, however many folks opt to remove it preemptively, which leaves the vehicle in v8 mode all of the time. We offer AFM/DOD deletes HERE.
