Replacing the shuttle valve doesn't require you to bleed the brakes. You don't go into the abs block or loose fluid. The shuttle valve is located on the bottom of the abs block and you can undo the 3 rubber mounts for the abs block and have enough room underneather to undo the 3 Allen head bolts and swap out the shuttle valve.

 

Oh I forgot, undo the wiring harness connectors. There is enough room underneath there you can fit an Allen wrench under and undo it without having to remove the whole abs block and save yourself a lot of trouble. That's how I've always done it and it doesn't take long at all

 

Underside view of abs block

Discovery Series II ABS Modulator Shuttle Valve Switch

 

Search for the "Option B" solution.

 

Plus one on the option b solution. Works great and u retain full function of all systems.

 

That sounds a classic symptom of the shuttle valve/modulator internal wiring fault where you'll probably need Option B as shown in the D2 sticky section.

It's around a 30 to 60 minutes fix and certainly not difficult to do. Don't forget to protect the engine bay paintwork and wing top.

In actual fact I didn't do the cut and splice method I actually bought a ready modified shuttle valve kit off of Ebay UK, it was expensive (£85) but a very tidy and effective option.

After fitting the new shuttle valves you'll still need to clear the stored codes with an OBD2 scanner.