What make and model car is it? Peugeots frequently get ABS sensor errors due to a build up of grime behind the mounting point of the sensor, pushing it away from the magnetic ring. Or issues down to the poor position of the ABS unit under the front wheel arch.
If it is a Pug I'll happily show you what needs to be done, FOC.
Mike Hurst gets a lot of praise on here but I've found they're not interested in tricky jobs, just the simple "bread and butter" type of work.