I'm trying to diagnose an electric problem w/ my O/D switch and shift interlock.
FWIW, see also my topic on "Failed shift interlock solenoid -- $635 ??!!" If you open the console, there is a wiring harness and connector where the O/D wires and (I think) the interlock wires go. You might want to make sure those wires are in order first, if the Instrument Interface Module is harder to access. (Or maybe that connector *is* the one you want.)
Also, my interlock solenoid (or related part) has failed but O/D still works fine, so at least they don't necessarily fail together, if this helps.