Just to relate what happened and how fixed ...

No previous issues or indications. Wife drives to grocery store about 6 miles from the house. Parks and comes back 15 minutes later. (Only non-linear environmental issue was the cold - about 15 degrees - at least for where we live in Northern Virginia. In garage overnight, though, so maybe only a contributing factor.)

Stuck in park on return. Wife uses the bypass mechanism through the console without issue, but does take some manipulating to get the detent pressed correctly.

Most discussions in this and other fora point to either the stop/brake switch and/or the shift module. Since the transmission shifted fine I was hoping it would be the switch.

Switch is easy to remove - pulled the panel under the driver side - three screws and nylon push clip at the bottom edge near the firewall. Also needed to remove vent cover on the tranmissio tunnel. Switch is nylon and black with two, single row electrical connectors mounted horizontally on the top and bottom of the switch near the top of the brake pedal arm.

Pulled connectors and let hang - they will retain their position. Switch has a pinch tab on the side. Pinch and rotate the switch counter clockwise and pull it out - yeah, not my first direction, either.

On examination of the switch, it appears normal - plunger doesn't feel odd - it has a self setting ratchet mechanism that sets itself on installation and initial brake application, I think. I pried it open and examined the three contact switch mechanisms - didn't seem to be anything out of the norm. Cleaned them with fuel system cleaner. Three small ridges on the internal slider of the switch operate the contact switch mechanisms. Only one of these ridges looked somewhat worn - i used pliers to squeeze the one worn ridge, hoping to re-establish the correct height.

Reassembled and reconnected and held in hand activating by experimenting with different positions - pulling out to full length and pushing at various pressures and distances. During this time, the shifter could occasionally be moved out of Park. I should have reinstalled to try it, but since I was pretty certain the switch was the problem, I called it a cold night.

Picked up new switch at American Service Center - they offer a MB club discount so total with tax was about $19.25 (on-line cost usually in the $13.50 range with $7-8 shipping) - switch is a very common item for many years in E class - "we sell a lot of these." Installed and works fine.

Sure glad it wasn't the shift module!

__________________
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg