I have a 96 grand caravan. about 50 k on a competely rebuilt trans. the other day service engine soon light came on, I checked and got 0703 code Torque Converter/Brake switch B Circuit malfunction,,. What exactly is this? Is this bad news or something a "shade Tree" mechanic could fix? Any help is appreciated Thanks!

Also, the tranny sometimes slightly shutters when coming to a stop, like at a stop sign. Like it sticks for a moment before down shift. Any Ideas on what the cause may be?
Thanks,
Scott