There's some misinformation on this issue around, and I finally figured it out, so I thought I'd post. Background: I've had the yellow Rear ABS dash light lit since my son did an emergency breaking maneuver as part of an accident he was involved in. I couldn't find a problem with the rear brakes nor the sensor in the differential. But I also couldn't seem to disable that light.

These posts helped me find the solution:
Can I disable/remove my 2nd gen rear ABS? | Pirate 4x4
ABS Removal
removing rear abs - YotaTech Forums

The solution is to unplug BOTH the ABS computer and the ABS relay.
The ABS computer is behind the glove compartment, up behind the horizontal metal bar. You'll need to remove two screws and a nut then pry/wiggle it downward, then you can unplug it. The plug release is on the top of the connector, which isn't accessible with it installed.
The ABS relay is fastened the passenger side of the engine compartment near the hood hinge with a single bolt. Unplug it.

I also removed the EFI fuse for a few minutes for good measure, but no ABS light on the dash now (doesn't even test light when the key is turned). I removed both components and electrical taped the plugs.