Vibi

Hi all,I have a 2013 C300 sport package. I have recently got error codes P0720 and P0721, and my car doesn’t move anymore. Despite the engine starting and running smoothly, the car refuses to move when I shift into drive, and the RPMs rise when I press on the gas pedal. On two occasions, the car randomly began to function again, and I was able to drive it for approximately 50km before it failed once more. Before coming to a complete stop, the RPMs goes up a lot to just reach a speed of 20km/h.

I am wondering if anyone else has encountered this issue and if they have any ideas about what may be wrong with my car. Thank you.

Odd Piggy

These codes inducate that the ECM is not getting useable information from the transmission. Indications are that P0721 is from a failed output speed sensor on the conductor plate. However, since P0720 is also present, a check that the wiring harness connector is not oil wetted and has continuity is in order. These codes usually result in the transmission going into limp mode (2nd gear only) but not complete failure to move. Since the car will not move at all, failure of solenoids or the valve body may also be involved. If you have a scanner and not just a code reader, viewing real time transmission data may allow a more precise diagnosis.

Vibi

I using the torque app, and believe it’s a code reader. What scanner would you recommend that’s budget friendly? Would icarsoft i980 do the job?

Odd Piggy

Many if the members have various iCarsoft scanners. Maybe one of them can comment. I’m not familiar enough to recommend. I have an 8 year old Autel that works fine for me. It was at the lower end of their models and I don’t have the add on attachments. When deciding, do get one that can be upgraded online by downloading.

mercs4life

Needs a new transmission oil pump and torque converter

Vibi

why would you suggest that?

mercs4life

Car is in gear, but you get zero movement. That sounds like no fluid circulation and no clutch engagement. My guess is the ears that drive the pump via the torque converter snapped. If you clear codes and get no hard faults from transmission, it’s hard parts that are broken.

Vibi

when I clear the codes, I’m keep getting a p0721 code. Is there a way to diagnose that the transmission oil pump/torque converter is gone? Also I just purchased a foxwell scanner if that helps.

mercs4life

If you can see live data, you will see input shaft reading rpm and output shaft at 0. That is a confirmation that there is no fluid circulating in the transmission. If it was a conductor plate you would get a bunch of other codes and you’d be in limp mode but still able to drive.

Odd Piggy

I get the impression that you have seen this before. MB tech? I’ve never seen a 0721 transmission error on a MB that was associated with failure to drive. I have seen similar on Chrysler transmissions caused by broken internal components disabling drive to first planetary set where the front pump was intact.

mercs4life

Yes I’m an mb tech, this is not a common failure. I’ve seen this happen 2 times in the last 8 years. 2nd time was my fathers car. It’s a fluke failure.

1Moonman

Hey!

I hope this finds you well. Did you ever get that issue fixed? What was the issue? When I read your post it's like you were sitting in the car with me. Haha

I got the same cods. Found it may be the catalytic converter. Now if it would need to be welded or replace the whole pipe.

Lmk thank you