Check ABS Control Module for codes
Faulty ABS Control Module
ABS Control Module harness is open or shorted
ABS Control Module circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
CAN Data Bus ABS Incorrect Signal is the generic description for the P1851 Audi code, but the manufacturer may have a different description for your model and year vehicle. Currently, we have no further information
about the P1851 Audi OBDII code.