Help with a PO140 code on a 1996 S10

First answer. Clearly your cat is bad. For a P0140 , the downstream O2 sensor is the messenger not the cause. Changing it did nothing. Cat clean did nothing (no surprise there). So the truck needs a new cat.

I use OBD apps on my phone or android tablet. There are products that can communicate with the ABS systems. Maybe look to ObdFusion