Two weeks ago we reported that GM would stop producing some of its 5.3L engines with active fuel management(AFM) and dynamic fuel management (DFM) due to the worldwide chip shortage. Today we have more information on exactly how those engines will be configured to accomplish that goal.
The company has released an updated Technical Service Bulletin (#21-NA-078) that sheds further light on exactly these AFM/DFM-less engines will be built and which parts are being removed.
It turns out the changes are entirely electrical. The ECM is being swapped while all of the hardware components of AFM/DFM will still be present inside the engines.
The changes only apply to 5.3L (L82/L84) engines equipped with 6-speed (MYC) and 8-speed(MQE) transmissions. Chevrolet Silverado and GMC Sierra pickups shipped with AFM/DFM deactivated will carry the RPO code YK9.
According to GM:
- Internal components related to AFM or DFM function will be present in engines; wiring, connectors, and fuses will be present in vehicles with RPO YK9. The ECM will not be capable of activating the cylinder deactivation technology.
- When diagnosing and repairing concerns with base engine or electrical function which may be related to AFM or DFM related hardware; utilize appropriate diagnostics within SI and replace any needed components as directed by the Electronic Parts Catalog; no changes will occur to AFM or DFM related components.
- Important: Any truck designated with RPO YK9 CANNOT be reprogrammed and changed to “Turn on” the AFM/DFM functionality.
This might or might not make potential buyers who wanted an engine without these features happy. Typically, problems with AFM/DFM engines happen because of the physical hardware, not the engine control module.
GM-Trucks.com is unsure if these fuel-saving features could be re-activated in the future with an ECM upgrade once the global semiconductor chip shortage is alleviated.