in automatic never a light. when I use the shiftable mode, occasionally the transmission fault light appears. no corresponding power or loss of anything. when i turn off the car, restart, and use automatic only-never a problem. whats the deal? thanks

 

It is the micro switch that is going bad. The transmission is mechanically linked in PRND (and 4th I think) to the shifter but microswitch operates the left side

 

+1 (from JTIS)
Transmission control switch:
detects the position of the selector lever.
contains two multi-track slider switches,
the upper track controls positions P R N D
and the lower track controls positions 5 4 3 2.
communicates with the TCM through the CAN.

It looks big, expensive and difficult to clean. It won't hurt to clean the connector though

If you haven't already it's well worth downloading JTIS from the HOW TO sticky at the top of this section