Hello all. My 2005 CLK 500 has gone into limp mode twice in the span of an hour. Searching suggests possible tranny fluid leaking into the tcu connector but I am unsure if this is also the case with the 722.9 transmission. I got under the car and found a connector but not like the one pictured in some of the threads. Id like to rule out some things before having it towed to a shop. Thanks in advance.

I think you posted this on the beznworld forum, too. Te likely culprit is a failed speed sensor. It's going to be a dealer repair due to the necessary coding when they replace the conductor plate and valve body.

I have a 2005 CLK500 as well and I've heard of limp mode but don't understand what it is? Can someone explain it?

When the TCU detects "something wrong" it forces the transmission into a single gear so this it doesn't shift, thus preventing any potential damage. The 722.6 will lock in 2nd gear, but the 722.9 will do different things. Sometimes is locks in 3rd gear, other times 4th or 5th depending on engine speed at the time of the failure. It will also prevent torque converter lockup.

Before this post, I thought 722.9 was introduced in 2006.

So, my 2004 CLK320 would be the last year for 722.6. This probably explains why 722.6 is so reliable since all the bugs have been resolved.

The 722.9 was introduced in 2004 on the S Class only. The 722.6 is indeed debugged. It went through many revisions with the only problem remaining being the electrohydraulic bush.

The TCU is integral on the 722.9.

The major early defect on the early 722.9 transmissions was the Siemens supplied conductor plate that was unreliable & typically gave "speed sensor data implausible" codes.

There was litigation between Benz & Siemens over this issue.

After the MY2004 S-Class intro, the 722.9 was then phased in. For MY2005, it was standard in the S-Class as well as the CLK500, E500, SL500, CL500, and CLS500. It went full mainstream to all non-AMG models in MY2006, then was added to AMG cars in MY2007.

Another fault in the early 722.9's are a bad main fluid pump (driven by the torque converter). It can sort of self-destruct. When it fails, it goes out with fireworks - it will coat everything under the car with transmission oil, and depending upon how fast the transmission is running, it can even spew "parts".

Yes ~ it's actually usually the TC bearing that fails & then takes out the pump with resulting mayhem!