Need help w/ error code

My wife's '97 XJ's CEL came on tonight. I took it to AutoZone and had the code read and it is P0700. It says "transaxle control system fault". The XJ has the NP231 and has the 4.0 and auto (AW4?) tranny. What exactly is this? Is it a possible bad sensor or did the tranny's computer fail? Everything seems normal - at least around town driving. I just want to know how serious this is - whether it's okay to drive around in or not. I have the next two days off, but I'm also doing a gear swap on my Z28, so I could get to the Jeep as long as it's not something that is terribly difficult or time consuming to replace.

i googled, P0700, and from what i have read says is a generic code for the tranny tcu and its not specific to any real problem. some with other vehicle but same code have had there pcm reflashed and the problem went away.

From the 1999 FSM:
"This SBEC III or JTEC DTC indicates that the EATX or Aisin controller has an active fault and has illuminated the MIL via a CCD (EATX) or SCI (Aisin) message. The specific fault must be acquired from the EATX via CCD or from the Aisin via ISO-9141."
All that just means a better code reader, or possibly a person better able to use the code reader, is needed.

EDIT: Do the reverse lights work when the code is on? If not, check your NSS.