How to join to stop error messages. You need to do 2 things with a code reader after joining the wires. Clear the fault code (5E5D for worn rear brake pads, this may show up as a problem under dynamic stability control so don’t panic MK60 E5) and also then reset the brake service level back to 100%. Eg pay for the excellent bimmercode app for this and all other error codes etc. You may also have had error code 5DE6 implausible signal if the wire has been playing up. Soldering is obviously more reliable than just twisting the wires together.