Did you know that it's possible to pull codes with the RABS setup!? Along while ago Iexperimented with it, I'm not sure anymore if I had read it in the owners manual or on the workshop manual?
ther is this place under the drivers side dash where a certain wire is dangeling, and you have to hold that to an earth point, and then (I thought) the OD light starts to flash.

Be aware, RABS is only a essay to prevent your rear wheels blocking and skidding if your truck is empty or just lightly loaded.

 

RABS is disabled when the truck is in 4wd. The system cannot regulate the rear brakes only when all four wheels are locked.

 

On my '93 the RABS diagnostic port was behind or under the glove box.
The only issue I ever had with the RABS that would translate into bad manners would be when the hydraulic valve failed and it would progressively tighten up the rear brakes and not release. You would have to wait hours for it to release. Rinse and repeat.

Now the early ABS that is in my '95 Bronco is an entirely different thing. I found that early technology to be SCARY .
If only one tire momentarily locked on ice the entire brake system would pulsate and braking action to ALL of the tires was reduced equally even if the other three tires were on solid ground.
Talk about not being able to stop the car-YIKES! It was like that from day one.