Greetings Mercedes enthusiasts and technicians. I am both but I am an Instrument Technician so maybe I can answer some questions about that area. I have had two of these machines and loved them both. I only have one now and finally after 204,000 miles she has developed multiple problems all at once. She is a 1997 E320 Royal Red, but it looks maroon to me.

Limp home mode:
P0715, P0720 both speed sensor circuits, installed new conductor plate and 12 pin connector, all solenoids click in and stay, installed both modules in the shifter , deleted codes. Still limp home mode. I haven't swapped out TCM yet to check. Think that could be it? My Autel MaxiDiag Elite 608 won't communicate with any of the mods, hmmmm.

Cylinder 4 misfire out of the blue this weekend, put new plugs in today, it needed it anyway, poor things burned a .060 gap. Started new at .032, No help stayed as a misfire.

So my techie mind said these computers need to be considered since they control everything except tire pressure. I took the water tight control mod center cover off and what to my weary eyes did appear, water all over the place fresh clean clear water, on the wires in the connector wells everywhere. So as I was disconnecting each of them to measure the pretty different colors of corrosion globs all up in the connectors and down in the mod pins. I did the best I could of cleaning them up, But gotta wonder if they are shorted out now.

Y'all think it would work to get junkyard mods and start testing the bad mod theory or just take it to the dealer tech shop. Keep in mind the trade in value on this beautiful machine is a whopping $700.00 US.

I've already spent that in the Autel scan tool.

 

Since I had replaced everything I could think of shy of towing it to the dealership, I decided to visit the local scrap yard. I found a 1997 E320 setting in the weeds with it's control module compartment untouched. Man sold me the Transmission Control Module for $10.00, I put it in my car, reset it and since it relearns shift points, after a few trips to town and back, soon my car was shifting through all gears. I saved $600 by not having to send my old one in, that apparently was through with controlling the solenoids, and having them flash a rebuilt one to my VIN. Which is nice of them, but I just found out that it's not necessary.