Its christman on my dash. Wheel speed sensor (ABS) intermittent with all lights, abs,downhill etc. How do i know which one it is? Will clean all harness connectors,any other ideas? How do these fail. Seems to be a phonic wheel and gear type. Not much to go wrong...

 

try doing a search for "Three Amigos" it is a common problem with disco. But without have the codes read there is no way of telling there are over a dozen reasons they code come on.
You will need a LR specific ABS reader to get the codes a standard osbdII will not help.