They also told me it was the throttle body that needed to be done if I have a new transmission were they lieing to me

 

What did they want to do for $1400?
How many miles are on it?
Is it an N/A or an SRT?
Is this the first time it has done this?
Have you recently made any mods to the car?

Try to give us a little more information and background ... and the use of some punctuation wouldn't hurt either.

RL

 

Conductor plate didnt fix my problem. I have another TCU that should be back from the tuner this week. If that is not it, next step is a wiring harness.

 

Read through this thread carefully. The most common know problem is with the electric plate that is a replaceable part right inside the transmission. This part has the two speed sensors that go bad and replacing the plate fixes the limp mode problem. Hope this helps. There is s series of great YouTubes videos that show you how to replace the electric plate. This plate is also called the connector plate.

 

Limp mode locks the transmission in 2nd gear and it will "bang hard" into gear when you shift it from Park into Drive or Reverse. Also the dash indicator will be just a black square (where it usually shows what gear you're in). If you have all of those things happening your transmission is in limp mode.

Now that we have that straight . . .

1) Check your fluid level. These transmissions are very sensitive to proper fluid level.
2) Remove the TCM (transmission control module), clean the connections and apply dielectric grease on the connector .
3) Check for and clear all trouble codes from the transmission and unfortunately you might not see any ECU engine code from a basic code reader. You might actually need to have a qualified Chrysler dealership (opps I think that may be an oxymoron) or MB dealer clear the code for you. Try to find an independent repair shop that specializes in German and / or Mercedes cars.
4) Lastly, I eventually found that I had a faulty automatic shifter assembly that was putting my transmission into limp mode. The previous owner apparently spilled some kind of liquid into the shifter mechanism. It was occasionally throwing the transmission into limp mode and only rarely threw a trouble code so it was difficult to diagnose.

Don't pull your hair out . . . that won't help. Let us know where you're at after checking the above.

 

I was lucky to have a great local transmission shop that had prior experience with this MB transmission. That is the key if you are not a DIY guy. I saw on the MB forum that there were two different levels of limp mode. Some threads talk about 2nd gear and others 1 st gear. Regardless, the solution is doing the steps outlined by Red Dog. The other internals of the trans are usually rock solid but the electric plate, gear shift spills and wiring connections will be the fist places to look.