I have a 2017 G550 and am searching for a full diagnosis tree for the distronic +, I have a really good generic scanner and it shows NO codes anywhere, Start stop works - so no battery malfunction. And it says Distronic Inoperative when I hit the stalk.

Any help would be appreciated.

Could be as simple as a sensor. Take it in, likely an easy fix. I've gotten those on several MB's overt the years and they usually went away on their own.

try this
first check your distance measuring- often it will not be working that’s what is essential to Distronic function

when driving - pass another vehicle and as you pass put on your blinker - you’ll get the caution light and beeps in the drivers seat. This will cause the distance sensing to reboot.
we have two G wagons: and if we don’t use the Distronic for a period of time - sometimes it seems to go into sleep mode.
I know it sounds crazy but it works -
good luck

I did this today and the warning worked fine on both sides. Then pulled the stalk to start the Distronic and got the message. Distronic Inoperative….NO codes, all systems Ok, but it will not engage, Guess I have to go to the dealer stealer to pay $1,000’s to do a 20 min job.???

Turn the radar off and on and make sure you are traveling over 25mph - if everything is working OK ( distance measuring ) then it should come around - get up on the highway