What color is the wire for the sub zero assist sensor
 

I have a cut black wire with a red tracer in the bit of harness heading toward the transmission. Is that what that wire is supposed to look like?

Sounds right to me...

http://foxed.ca/rx7manual/manuals/WI...2088%20rx7.pdf

"sub-zero motor" page 33

...or if it's going towards the transmission it could be the reverse lights, try backing up :) .