Bosch ABS 5.0/5.3 ECU comms

[Scott@FP]

Does anybody know the nature of the ABS control unit to ECU comms for Bosch ABS 5.0/5.3 (AWD)? Single wire comms, I get a 50% DC pull to gnd at about 2 Hz from the ABS unit. Not clear whether this app (99 Audi A4Q) transmits torque to ABS or any signal back. Reference material I have access to is very vague.

Thanks,

Scott