2007 S550 Won't go more than 25mph, but ok after restaring. Help Please.
 

I have a 2007 S550 4Matic, 78k Miles on it, came to a stop light waited for green light, as it turned green my S550 bearly accelarated, got up to 20-25 mph and would not go more (pedal all the way down), I stopped, tuned it off, waited for 30 seconds, started the car and it was acting normal, no CHECK ENGINE light or any other lights came on, please help me figure out whats going on, my transmission shifts good (no problems there). Please help, THANKS in ADVANCE!

Scan it with DAS to pull the codes. (there may be codes stored even if they don't show on your dash)

Could be conductor plate or valve body. When you pressed the accelerator when the light turned green, did it feel like the car was starting off in 3rd gear??

Yes it kind of felt like it was in a higher gear.

Yes it kind of felt like it was in a higher gear.

Read more: https://mbworld.org/forums/s-class-w...#ixzz32UQbbNRE

Bring the car to a good indy that specializes in Benzes and have them scan the car. If it is the speed sensor code, you'll have to change the valve body or hopefully just the conductor plate. Search around this forum, there are lots of threads on this. You have a 722.9 transmission.

Is it in Sport Mode?

Thanks! I will take it to my MB mechanic to scan it. Thanks again.

No it was not in the Sport mode.

Got it checked by my mechanic DAS showed: Y3/8n2 Internal Speed Sensor VGS. He tried to connect to Transmission Control Module but it din't connect, it kept showing that there is a connection problem, could the actual Transmission Module be bad? What should I do re: Internal Speed Sensor VGS? Please advise me, thanks everyone in advance!!!!!

Here is a picture of it.

Like I said: "If it is the speed sensor code, you'll have to change the valve body or hopefully just the conductor plate. Search around this forum, there are lots of threads on this."

What did your mechanic say after he saw the fault on DAS?

"Will that be Visa or American Express?"

I didn't have to pay him, he is my good friend :) He said that it might be Speed Sensor.

Ahhahahaa good one mike

Alex jokes aside you most likely have a conductor plate failure . Yes you can replace just the conductor plate and not the whole valve body assembly. If it makes sense to you to replace valve body it comes with the conductor plate. I would not recommend driving it , could cause further damage. Make sure the tech checks the fluid to see if it has burnt up or if lots of metal shavings are found. If not replace the valve body or conductor plate , change the fluid and filter obviously , reprogram and get the show on the road ! Goodluck my friend

Speed sensor is part if the control unit and it's internal. There are a lot of transmissions that have external speed sensors. Not the 722.9 7 speed.

So, the Valve Body can only be replaced at Benz Dealer or I can buy the part (I have wholesale account with benz dealer) and have my mechanic replace it? Dose it have to be programmed? Guys thanks a lot.

Mercedes had it before where they are the only ones who can sell and install that part. This is considered a "theft related part " so that was one big reason for there policy .I think that policy has since changed , call up your local dealer and ask. If you do a Google search there are also a few reputable repair places that will repair your existing valve body and or conductor plate and ship it back to you in a timely manner. If you replace with a new unit then YES it has to be reprogrammed. The vehicle will not function at all without correct programming .

Ok, got it. Thanks everyone! Will let you know what happens.

Replaced the cunductor plate, codes are gone! Back on the road! Cost me $800 (parts & labor), thanks everyone!!!

Wohooo!! Lol good job alex... I hate it when ppl get ripped off . I'm happy you tackled the problem with no headaches !

Dealer would have been thousands !!

I took it Benz dealer that I had hook up's with, full price for this repair is around $1,700

When I called the dealer for mine, they wanted close to $3,000 because they wanted to change the complete valve body. Brought it to an indy and he changed just the conductor plate. He charged me around $1,300 i think, so you got an excellent deal at $800. It's still an expense that you don't anticipate with a car like this though. I have some work trucks with close to 300,000km and have never even changed the tranny oil in them and they run fine. Some of these Mercedes 722.9 trannys need expensive repairs even after 50,000km. Crazy!!! Whoever designed this transmission should be shot :violent:!!

I am happy for you alex denver
I also appreciate your feedback that may help for anyone with an exact issue
Have a good weekend :y