i am having a hard thud when downshifting coming to a stop on my 2000 auto maxima. i have read in a few places but had no help that it could be the solenoids or the TCM. i performed a TCM SELF-DIAGNOSTIC PROCEDURE (NO TOOLS), found in the fsm, and the O/D light stays on. the fsm says that this could be Park/neutral position (PNP) switch, overdrive control switch or throttle position switch circuit is disconnected or TCM is damaged. how do i distinguish what it causing my problem? any help would be appreciated.