hi i am shannon i will help on this issue
dose it shift ok after it warms up?
if it dose you most likely have hardening seals in the trans.
some times this can happen if the trans gets over heated
or if the fluid has not been serviced
the repair is to have the transmission overhauled
but i would try a chemical repair first.
i like Seafoam trans chemical
add the can to the trans fluid drive for 20 miles
then let sit over night
test drive in the morning if the shifting has returned to normal then have the trans fluid flushed out
be sure at lest 12 quarts of fluid has been replaced. if the filter has not been done this would be a good time to service it too.
then put 1/2 a can of the Seafoam in the fluid to keep the seals soft.
both of these cleaners are good . i would use ether one
i see you are offline . please post any question in the box below i will respond.
hear is a diagram that shows all the fuses that work the shift interlock.
this is the whole wiring diagram for the interlock system. i split it in two to make it bigger just print band tape together.