problem: suddenly couldn't move our 2002 midbath out of park.
solution: According to the mechanic, there is a part that tells the computer that your foot is on the brake, which then allows you to shift. That part has a spring. When the spring breaks, it's Motorcraft SW-2217 E9TZ-13480-A. It wasn't even an expensive fix! Quite a relief.
Thanks for posting the solution, Wendy!
It's an unusual problem I have seen once on a 2006 MB.
Either the brake switch or the interruptor solenoid fails, locking the transmission in Park.
One set of contacts in the brake switch activates a solenoid that releases the shift linkage, allowing the transmission to go into gear.
https://www.oreillyauto.com/detail/c/motorcraft/engine-sensors---emissions/body-switches/brake-light-switch/416768908ca1/motorcraft-2-terminal-multi-purpose-switch/mot0/sw2217
More Information for STANDARD MOTOR PRODUCTS SIA1 (https://www.rockauto.com/en/moreinfo.php?pk=12770629&cc=1385119&pt=16116&jsn=1015)
Glad you got it fixed.
Larry