I finally clean out the old factory ecu and and engine harness. I would like to get the tach to work again. Does anybody know how this is done. I think I need to use blue red wire (1m) and hook it too the trailing ground.

 

The FSM shows the wire Y/L (F) which I think is yellow. Trying to find the aberviations on the fsm right now.

 

My car is S4 auto

 

Yellow/blue wire at the instrument cluster to the yellow/blue wire at the trailing coil.