i would first try checking the atf fluid, then i would try to clear the engine light and see if u stil have the trans problem..if it comes back then i would conduct another test of the solinoid because out of all the cars ive had in the past with trans problems, they all started with sliping or thumps.. with only 86k on that toyota i would check the simple things such as solinoid/ atf (drain and fill) good luck with the fix!