I have a e39 (2000) the abs light came on and speedo stopped working also all petrol dials going up and down as you go through gears.
I got a mechanic with a bmw code reader (cost a small fortune) and it said n/s rear abs sensor at fault i replaced the sensor and problem still exists some times it works fine for about 10 miles then radio drops volume and lights come back on.
I was told that n/s and o/s sensors are the same and to swap them over to see if that cured speedo as i'm told speedo works off that same n/s sensor,Have just tried that and speedo still not working.
Please if you could HELP!!!
Thanks John.

JONNY BIG WHEELS, June 2009

Had same problem - turned out to be the ABS module - effected by engine heat - fine wires inside that link to the circuit board open circuit. Lots of info on web. Also quite few companies that can repair (£100). Then needs recoding...

ABS wheel sensors operate -

Radio volume (speed)
Cruise control
Speedo
Automatic gearbox changes (goes into limp home mode)

Can be a DIY repair by soldering - was beyond my ability though.

John, February 2010

Had same problem with my 1999 520i . Ended up being ABS control unit !! Not cheap, tried locating used part but due to variety of systems fitted was out of luck and time (MOT) Part fitted by BMW cost approx. £700 !! Good Luck .

Gaz, June 2009