ABS AND SERV LIGHT ON ALL THE TIME

The ABS and Serv light will not go out, so far the mechanic has checked all the ABS sensors and reluctor rings and no fault codes were showing. He then sugested that thw ABS pump ECU was faulty and not picking up the details of the faults from the sensors or the abs ecu was faulty.

This abs pump/ecu has been changed and abs light and serv light still on all the time. and he says he is still not getting any faults on fault code reader. Can anybody help please at my wits end.

Thanks in anticipation