SM-JC41 Di2 frame internal junction box

The frame junction box connects via SD50 E-tube wires to four different points: front derailleur, rear derailleur, cockpit junction box, and battery mount.
All Di2 components on the bike require the same firmware version. Using Di2 components with different firmware versions may cause malfunctions.
Use the Di2 system checker to update component firmware from http://e-tubeproject.shimano.com/