Weird thing happened while driving.
Was going about 55 mph when all of a sudden my disco kinda just hit the brakes on its on.
then I had the brake light and p1590 code pop up.
any ideas?

 

Wheel sensor issue. Get hold of a code reader that can examine the ABS system to tell you which one.

 

I've had this issue for ever, along with the "3-Amigos"; I had brakes codes checked once with a specific reader and should have what came up laying around; I'll look for it to compare notes. Apparently some issue with ABS, plus a mechanic broke driver front sensor, but haven't replaced it yet, although I have it. Supposedly my ABS is not working, but I think I feel it engaging at times when braking, so most def will take the time to check again. But yes, vest course of action is having those brake codes pulled out. Please share your findings.

 

Both rear sensors were showing low output
also an ecu ground or reference ground fault

 

Check the wiring from the wheels sensors back to their connections to the ECU. If all looks good, replace the sensors or (probably simpler) replace both rear wheel hubs.