René, wires colour coded YU = yellow/blue do not all have the same purpose. The colour codes and numbers should all have matching codes at the other end of loom cable.
YU20 in engine loom is one side of trigger to injector cylinder 1 so likely not relevant.
YU85 in engine loom becomes YU122 in chassis loom and is ground trigger from ECU pin 106 for the ignition relay (the middle one). You measured battery volts on this ECU pin but I suspect this was on matching ECU plug pin whilst disconnected, so your high impedance meter was measuring permanently live feed back from other leg of relay coil. The important thing is that the ECU should ground this line when ignition switch is turned on hence triggering relay.
Apologies if I've missed it but you still haven't told us if this important relay is turning on with ignition, although I know you have replaced it. Can you check with a multimeter engine fuses 12 - 16. All five should read battery volts when ignition is turned on as previously suggested.
