Sorry if this has been asked before, but I have been trying to find the source of this issue for awhile.

2001 GS430 with about 210k miles. Drives pretty well, but I am unable to shift into the lower gears (past D). Works normally from Park thru Drive, but I feel a hard block when trying to go lower than Drive. Considering I don't any error codes pertaining to the transmission, I'm led to believe this is an issue related to part of the shifter assembly. Any and all input would be much appreciated. Thanks everyone!!!