I found in one manual where it says that BY is actually referring to BR. Not sure if that helps because I don’t see a BR relay in my print either. The 704 fault says DBD fault though so I think they’re referring to the DBD input that comes from a N/C UD and N/C S1 & S2 contacts. There’s also a DBD2 input on the IOBD that comes off another set of N/C UD, S1, S2 contacts but don’t think that one would give you the drive faults.
