110amp alternator

Would anyone have one of these to check on my 04 wrx special. Engine management light is on and throwing up code p0559. Had the alternator checked and wiring by hamiltons. Said alternator was grand and maybe a 110amp could sort it. If not ill hav to get the ecu fixed or replaced, thanks fellahs

Is the alternator thats on the car the correct amp?
Have you checked your Earthing points?

Yeah 90amp on it and bought another one to try but no luck, also a new earth ran aswell