On my 2000 DII, my abs light as well as traction control and downhill descend lights all came on. I took it to auto shop and they read the code which came up with DTC P 1590. According to them, this means the "hardware is okay, but SLABS ECU is sending error. This occurred for traveling on rough terrain."

And something about... measuredat ECM 40 PIN connector CO637 Number 34 (Red/Green wires)

How do I fix the lights an get them to go off?

 

1590 is not really an "ABS" code per se. It is an ODBII code for a rough road fault that the computer throws when you have an ABS code. You need to get your ABS codes read to see your real fault code. FYI you will need to go to a shop that has an ABS diagnostic scanner. Also note you need an ABS scanner to clear even the 1590 code.

Edit: Also not sure what C0637 is. Go to a dealer or a shop that knows Discos. You can also buy an ABS Amigo for $200 or a Hawkeye for $650 and DIY.

 

Read my reply I sent to you.
Are your brakes squeaking, if you do a panic stop from 30 MPH on a loose surface road, do you feel the ABS pulsate thru the brake pedal?

 

Sent you my contact info. I was feeling the ABS pulsating, but then I had both front and rear brakes replaced. I still feel ABS pulsating very very lightly every now and then.

 

Sounds like maybe a bad shuttle valve. Get your ABS codes read you will not know anything for certain until then, just guesses. Most of the ABS codes will disable the ABS. A bad shuttle valve will not disable the ABS just lower the threshold for activation.