RS6plusMTM

Your picture is a bit too close to gauge the wire thickness, but If you've tried the obvious like a missing ground to the neg on the battery, I think there's another ground that attaches to the starting motor - I would look for a broken connector somewhere as the end you had would of been attached to it

This is for the TDi engine/gearbox, but it will give you an idea where to look
A = the selector arms (the adjusters are on the end)
B = they attached to these ball joints on the gearbox
C = this arm can be use to manually move the gearbox selection by hand