Speedometer and milage gone off today while I have been driving any idea what it could be in the old days would be cable from the gearbox to dashboard I guess it's electronic on these

There is a sensor bolted onto the housing at the back of the gearbox, one bolt, easily changed with pit or on ramps, maybe just a fuse gone on plug come off

Undone the sensor with that 22mm nut but the pin is still sticking out of the gearbox there seams to be an Allan key at the side is that holding it in like a grub screw?