Re: 04 KJ trans issue
Not.familiar with the KJ, do you know which transmission it has? The P0700 code only tells that the TCM has set one or more faults, its not a failure code of the TCM itself. P0731 is a code which is set when the ratio between input and output speed is not as.expected, which normally means a slipping clutch pack, but could eventually be caused by a problem with one of the speed sensors.
Depending on which transmission you have, i could maybe tell you a bit more.
But first thing, did you check the fluid level and smell the fluid for burned smell?