I did a search and found this is a common problem with Discos but never really found a solution.
I have a 2000 Discovery II with 66K miles that I recently encountered a problem with – the Hill descent, ABS and Traction control lights all come on at the same time. Once they come on, they stay on till the truck is shut off. When you start it all is well – no lights but they will come on minutes later or days later. Once on, they stay on until the truck is shut off.
I took it to the shop and they replaced the "shuttle valve" but the lights came on the next day. Now they tell me I need an ABS Modulator at the tune of $700 plus labor. My breaks, traction and suspension seem fine. Does the ABS Modulator really need to be replaced or is there something else wrong?
Thanks in advance for your help.

 

Not finding a simple solution for the "3 amigos" is common, as is the dealer going for a $700 repair. My problem went away when I did a much needed complete brake job (pads, rotors, fluid change, and replaced one damaged rear hub). I have read others have found it to be a faulty wheel sensor. Search "3 amigos" and you will find much to read.

 

Start with your brake pads, are they worn to thin? Next check your ABS sensors. Misaligned or a bad ABS sensor will cause this too. if your ABS modulator was bad you would have a hard time stopping.

 

Yes, a bad hub can cause the three amigos too. As can too much brake dust on the wheel sensors.

 

If the shop is reputable, you may be looking at a new modulator. The codes should have pointed to the shuttle valve. For many, this is a fix, and sometimes only temporary.... Call the shop and see what the ABS codes were that you got. Post them on here, and Mike can tell you what they mean..... Might be looking at bad news....sorry

 

Mine does it if I go a week or so between washing the brake dust off the rotors, pads are still good though