I have the same problem. I still have not found the diagnostic wire. I still am not 100% sure if I have rabs 1 or 2. It's a 92 f150. At this point it's either start shotgunning parts or deactivate.

 

Take out your RABS computer and look at the part number. F2TF-2C018-AA is RABS I

I'm trying to find out what the difference is, so far I only see wiring diagrams for RABS II and what I am reading doesn't even mention RABS I. Almost makes me think RABS II is just the second version and might work with RABS I but I'm not sure.

 

I used a RABSII computer and it's fixed my problem. Been driving it like that for the last two days, no issues. Before I installed the new computer I did verify I still had the problem with the old computer