I had the exact same thing happen to me this past weekend on a trip from Dallas to Houston, with the avg outside temp at 102 during late morning. Stopped for gas, restarted the car, pulled into the ramp to enter the interstate, and realized that I was locked into 2nd gear -- kept going about 1/4 mile until I could safely pull away from the interstate across the ditch onto the service/frontage road. Called MB roadside assistance, and they offered flatbed tow service for an arm and a leg (no complaints -- it is what it is), but 15 minutes later, the transmission simply reset on its own!! It was like a Microsoft Windows PC where I just rebooted and everything went back to normal!!!

I came back, took 98 ML320 w 116k miles to the dealer for a computer readout (after first having gone to Autozone for a complimentary OBDII scan which showed problems with ETC and EGR), and it showed about 16 different error codes. It was worth paying the $110 for the computer readout that gave me the detailed error codes.

Dealer quoted me $900 (parts + labor) for replacing the TCM, and $400 for EGR. These were estimates, without a guarantee that the problem would be fixed!

Then I sat down at the computer and started going through these forums and realized that potentially it was the gear recognition switch. Picked it up from the same dealer for $106.25 + tax (part # 210-545-13-32). Opened up the TCM, replaced the part -- BIG THANKS TO DAVID COOLS & GILLY for help -- took 6 hours total. No problems -- didn't have any parts left over after putting everything back together. Noticed that there were spill stains inside which means there was liquid that was spilled through the shifter opening.... sticky and dark which means most likely soda pop.

I still need to go back to get the computer reset to erase all the codes, but the CEL is off now, and haven't had the limp-home mode repeat. Unfortunately, I was alone at home and with the insane amount of grease on my hands, I did not take any digital pictures, but can tell you that there are plenty of moving parts inside the TCM that need to all be "set" properly as you are closing it back otherwise it will not close.... That is what took me over an hour.... but otherwise it was not a bad experience at all. What took me about 6 hours is rightly billed by dealers at 2.5 hrs -- if the mechanic knows his/her stuff, then it would take just about 2 to 2.5 hours to do the whole thing. The only challenge I had was that the dealer wasn't willing to replace just the gear recognition switch but wanted to replace the entire module.

Anyway, I'll post an update to this forum after I've reset the computer (anybody know how to do it without needing a star computer?) and let you know how things go.

Thanks to all who contribute to this forum -- makes the internet worthwhile!

Cheers!