Whatever the problem it will have to be repaired at a dealer.

The pre 96 ABS designs were completely proprietary and Chrysler
did not release interface documentation to the scantool manufacturers,
you cannot even bleed the brake system without a genuine Chrysler
DRB scanner.

The ABS design in 93, 94, 95 were the Bendix 4, the design is fine.

The ABS design prior to this is the Bendix 10, the design is a.s-backwards
and although you can keep it running, it will consume repair parts on a
regular basis.

How many miles are on this and what are you looking at paying?

It's not a common failure for ABS in the 93, 94, 95 series of vans.
I'd suspect some shadetree mechanic replaced a caliper or master
cylinder and didn't take the vehicle in to be bled at the dealer, or
they didn't periodically flush the brake fluid and water got into the
system and corroded the lines.  Is there any fluid leakage in any
of the lines?

This could be a pretty spendy repair.  If it was me and I got the
van for free I might take it, gut the ABS system and replace it
with wrecking yard ABS parts, then take it in for bleeding and
cross my fingers.  You really have to get under it and take wheels
off and such and really look closely at the condition of all the brake
lines, calipers, etc.

Both my 94 and 95 T&C's have original factory ABS, no problems.

Ted