I don't believe the trans temp is reported by the PCM for the 99-04.
IIRC, the 05/06 PCM reports the trans temp since the TCM is integrated. That integration is also why the 05/06 PCMs have a higher failure-rate due to excessive heat (which the WranglerFix PCM resolved for me).
Edit: In case you are interested, Blaine brazed a bung into this
Dorman Pan (with drain bolt) that I purchased and had shipped to him. I had that done and connected an
Autometer (z-series) gauge to it before I owned the obd2 gauge. It worked great.