I had issues with AC intermittently not blowing and the above code in the AC System showed with my iCarsoft scanner. The following thread on the w166 forum had all the answers, notably the last post with print out and instructions: https://mbworld.org/forums/m-class-w...012-ml350.html

I ordered the Wago connector as mentioned in that thread and knocked it out Sat morning. I unbolted the four bolts that hold the seat, leaned it back (did not disconnect seat wiring), removed door trim and kick panel, and three bolts for plastic cover under carpet. I did not fully remove the carpet due to time constraints, but peeled it back as much as possible in addition to the plastic panel. I was able to reach the AC connector, and while I didn't have the ability to remove the wires from the connector to reroute through the new connector, I straightened out the pin of the AC wire, tightened it, and reconnected it. I started the car and it worked. So, seemingly it is fixed without the new connector, and the existing one just needed a little refastening. Put everything back and I'm now properly equipped for the blistering Southern summer heat.

No problems so far and driven several times, we shall see.