2003 Buick Rendezvous trouble code reads P1887B

Since you have a direct code like that, I would have a reputable trans shop do the repair, that way if there are other issues later, they have record of what has been done.They will/should also test the circuit to be sure the wiring is all good, and that i tis just the solenoid/switch

can you tell me if the switch referred to is on the inside or the outside of the trans case?. the reason i ask; i bought the car from an estate (15,500 miles on an '03). the owner lived in a rural area of central texas. there were obvious "signs" that some type of rodent had spent time under the hood. i looked it over for wiring damage and found none. the light went out for a few days, then came back on one morning on the way to work. i am an i-car platinum certified tech, so i have some mechanical inclination.
what would you do if it were yours???

The TCC solenoid is inside the trans.If it comes adn goes like that it could just be a sticky valve/solenoid.Honestly if it was mine i would have a trans shop do it so they could use a break-out box and manually apply the solenoid to make sure it is all working properly