Td5 abs

Just test driven a disco11 td5 and i had the abs and hdc lights come on. I took it to a mate of mine and he plugged it in to his box of tricks. The fault was listed as potential wiring fault or sticking /faulty shuttle valve.
Anybody come across this one,can the valve block be refurbed if that is the problem.It doesn't do it all the time and the fault does clear when the engine is switched off.Any ideas.

Given that the fault is intermitent then I'd look at the sensor wiring and related first.

Thank's Andy, i've just agreed to buy it and that will be the first thing i check.