Have a problem, The ecu relay seems to have stopped working, i've traced the problem back to pin 10 on ecu(its the negative path to the ecu relay). When i connect a negative straight to relay the car starts fine, it seems the ecu is not outputting a negative so to speak.
Why does the negative route through ecu in first place, is it for safety, engine cutout ? overboost protection ?
Why would it stop working ?

Cheers all