GReaN

204.080 - C 300 4MATIC

The front propeller shaft took a crap and had to be replaced, the car sat for a few months until i had the time to do it. Replaced the front propeller shaft. Work fine for around 100 or so miles, After a heavy rain storm for off and on a week, I realized the carpet was soaking wet... not just damp but like big puddles of water! WAY TOO MUCH water!!! mostly on the drivers side but water definitely was on both. I shopVac the majority of the water from under the carpet the best i could and the carpet dried out the next few days. Turns out the sunroof drains where clogged for who knows how long, fixed the clog and everything seemed to be okay. the car worked fine for a few weeks not really driving much anywhere, but nothing unusual form my few trips around town. changed the motor oil , and got a new Auxiliary battery.
A few weeks go by, while driving down the road going around a corner the car felt like it went into neutral and had to get it towed home. NO CHECK ENGINE LIGHT came on..nothing waiting for the tow truck i thought that maybe the shift rod thing maybe came loose. (i had to remove the shifter rod linkage to drop the trans to replacing the front shaft) but it looks fine after i checked it. The drive shafts do spin ( at least the front one spins when in reverse & drive. stop spinning while in park and neutral) I can see and hear it spinning when in gear. I also notice that when i shift to reverse and drive, the car moves a tiny bit, not enough to go anywhere. doesn't kick or clank or anything like that, car just moves ever so slightly & revs as if in neutral.. so...

SIDE NOTE- I recently decide that i need a " professional " scan tool but I really don't know what or how to understand all this information, I am still learning how to understand this information and how to better diagnose problems using a scan tool this advance.

All that being said, I know my way around cars and been working on them since a teen. New to using a scan tool, i can use a little help with this issue.
Hooked up my scan tool and this is the report.



The D138 code and all the other codes has been there before the proplershaft went out, so i'm assuming its unrelated, 0720 is the only new one.

my (un)educated guesses are:
1. output shaft sensor just decided to take a crap ( code: 0720 ) like it says it is. (strange time for it to just decide not to work anymore) i found different results searching "0720 mercedes benz c300 ".output shaft sensor, output speed sensor circuit , even a Wheel speed sensor causing this... hmm , not sure which one is the correct one.
2. Water corroded a connector or two under the carpet. causing it to throw the 0720 code, Very poseable..
3. umm, the car hates me.
4. dirty/ old/ low trans fluid ? it's was about that time... no leaks.
5. something i don't know about yet ??
6. installing the new auxiliary battery caused some kind of problem ... properly not.. i have read that these cars get weird if you install new batteries without resetting something with a scan tool... mayby...
7. needs new transmission... it was just it's time to go ☠ . ehh , maybe.. no sings that i noticed that indicated it was going out.