DrMattyJK

My 2020 C43 randomly goes into a 'neutral' condition despite being in gear. I was able to grab my phone and catch it in action. I am in drive, C comfort mode, auto stop/start off. I can't put the car in gear without eventually cycling to Park then Drive again.

Look at the top of the cluster and I am not in any gear. If I were in neutral it would have 'N' at the top. Eventually I get it in gear and it goes into '1'. Very distressing when it happens!!!

Car is at the dealership (again). This car has been a problem ever since new.

Any help would be appreciated!!! No trouble codes thrown, no symptoms or signs it was going to happen.

W205C43PFL

Sounds similar to this: https://mbworld.org/forums/c450-c43-...-redlight.html

W205C43PFL

nevermind you already posted there sorry I wasn't able to help.

DrMattyJK

Exact same thing. Yeah, no help ever came out of that thread. I have a video now.
Dealer downloaded the trans data. No trouble codes thrown. They are sending to Germany.

Thanks though!

W205C43PFL

You're welcome, I do recommend trying a different dealership if yours is not able to find the solution to the issue.

DrMattyJK

So some progress. They seem to think its the torque converter. It seems to me though that a TC problem would be slip during acceleration or shuttering at a crawl speed. My trans randomly freewheels like its in neutral. No other symptoms.

Does this make sense to everyone??

I'm just worried that the whole things is taken apart to put in a new TC and then we find out the box is bad. What a waster of time.

M

W205C43PFL

Hmmmm

W205C43PFL

Sorry about this but I don't have any advice that might be worthwhile, I guess you might need to proceed with letting them take it apart.

W205C43PFL

Any luck with the repair?

DrMattyJK

Still working with them. No trouble codes so it’s a real problem for them.
I adamantly disagree that it’s the the torque converter with them. It’s impossible for a converter to do neutral randomly. Only when it’s completely blown up and slipping the entire time.

Interesting is the car is not in gear on the upper gauge cluster during the event. Only once it’s back in gear does ‘1’ appear after I have gone to Park and back into Drive.

Strange! All I can say is I know it’s not the torque converter in my opinion.

W205C43PFL

I mean you got a point. Hopefully they figure it out.

W205C43PFL

OP, I forgot to ask did they check the ISM? Intelligent Servo Motor as that is responsible for shifting behaviour, yours might be defective, if not also ask to check the transmission mechatronics, good luck getting it sorted!

DrMattyJK

It's the 9gtronic transmission. Not sure if it has a ASM like previous generations. I agree though that it seems like a module problem of some sort. The transmission "thinks" it is doing the right thing hence no trouble codes. Why? Sensor, sticking valve/solenoid, programming are all possibilities in my opinion. How to solve? Replace the whole thing in my opinion.

I've had the issue since new and they've tried reprogramming and tried various things. Mostly though they didn't believe me till I got the video! It has stumped the engineers in Germany. They like: "It can't be". It is though!!!

W205C43PFL

Yes I am aware what transmission you have, the 725. So yes it is still highly likely it has the ISM. As for swapping the transmission altogether, one thing is if they replace it with a reman transmission, you should consider it for a while. From my experience with reman transmissions they aren't exactly perfect and isn't exactly like a new one, although your experience might be better.

DrMattyJK

So just an update for anyone interested. The torque converter was replaced and surprise surprise, the neutral condition happened again.

I have learned a lot from this car and it is a bit disappointing Mercedes' overall handling. I do understand that I lucked out with a very unusual car and there seems to be no other cases out there. I've brought the car in and out over 20 times with video proof of the condition. Everything to avoid a replacement has been done. Module, reprogram, TC etc. Finally, they are going to replace the transmission.

The trans appears to get "stuck" between 2 and 1 and it goes into a blank gear condition. The best I can explain is that no trouble codes are thrown because this planetary set or switch is not monitored by the module for this possible condition. According to Merc, if there is no trouble code, there is no possible way for a problem. There is usually some discretion at the dealership on options to deal with difficult problems however with these 9speed transmissions, any issues go to Germany and they follow a very specific repair algorithm from their engineers. Even to the point of being completely idiotic like replacing a TC despite it not explaining the situation in real life and protest from the actual tech at the shop.

I suspect this will fix the 2-1 clunk that I have as well. I am quite aware that these C43's shift firm on purpose and are a bit harsh (not a bad thing for a sports car), but mine is definitely out of spec. Imagine the shift slamming into 1 sometimes where you immediately to in the mirror think you we rear ended. That ain't normal!

Will report back after the job is done!

W205C43PFL

Glad they finally caved in and are replacing the transmission, will it be a new one or a reman?

exarkun616

I had this happen to me this morning as well. I was on cruise control at ~70mph and it suddenly revved to redline and I had to pull off and restart my car for it to go back in gear. Like you said it goes into a blank gear mode until restarted. I have had this happen 2 or 3 other times too but never on cruise control which is very concerning to me. I am very curious to see if your issue gets fixed by a new transmission. Did the problem get worse over time or was it mostly one-offs? Best of luck to you!

DrMattyJK

Report it to the NHTSA. “Random neutral condition” is the best I can describe it. Only way to get a recall or determine how wide spread the problem is.

Would happen pretty consistent about once a month, maybe 2 months. Only when I came to a stop for me. Green light, no go and people honking at you.

Digging deeper into it, the techs say off the record that the “sail” mode, when you’re in individual mode (US) or Eco (other markets) can activate inappropriately “under certain conditions”. It purposely goes into neutral to decrease engine braking saving you fuel.

I’ve had my trans module replaced already and it still did it. Merc did not believe me and literally said it was impossible. Set up a GoPro or do what you need to prove it. I proved them wrong.

Folks should monitor the gears. Keep an eye if it ever goes “blank” under conditions. The more I looked, the more I noticed brief period where it did it.

exarkun616

That is really interesting. I just reported it to the NHTSA as you suggested so hopefully more eyes get on this. That is interesting that it was only when you came to a stop. For me it has always been when I have been driving and it drops to neutral. I was in Individual with the sail mode on but I would have thought that cruise control would not make this possible as I have never seen it go into sail mode with CC on. I really like the coast mode but if it continues doing this then I will definitely use comfort mode instead. I'm sorry that yours has been so consistent but I do appreciate your transparency and info on this. Are you going through warranty on this work? I just bought my car last July without any extended warranty so I am terrified of this becoming a transmission replacement service. Thank you again for your posts about this!

DrMattyJK

Not sure your warranty situation but take it in to document the event. They should look for any trouble codes and see if there’s a reason for your problem.

There are consumer protection laws (Magnusson Moss) out there. Even after warranty expires. You have to give them a reasonable chance to fix things. If they do not or it gets ridiculous, you can sue. Don’t expect more then 10-20% of the purchase price. Probably would cover the cost of a trans IF you need one.

I looked into it and have a firm that says my situation is an open close case. Still debating pulling the trigger. I really just want a car that works!! I also feel a lawsuit is bad energy for me. The car companies really don’t ‘care’. This is part of the business. Funny I’ve had to buy a Mercedes to find all this out. Purchased many many cars (all brands) and really never ever had any issues.

W205C43PFL

Sorry to hear that, what year is your vehicle and what mileage does it have, any transmission fluid service done yet (depending on mileage)

W205C43PFL

I think I asked previous already but this happens in all modes? Reduced, Comfort, Sport, Sport+? even manual? Auto start/stop set to on or off?

W205C43PFL

Hopefully a software update will fix your issue but what did you set your individual to? Does it happen with auto start/stop on and in Reduced mode (I think that is how you enable sail mode in reduced, by having the auto start/stop button activated)

W205C43PFL

Good call on the consumer protection law, is it by state though?

DrMattyJK

Lemon laws do vary by state. Magnusson is federal. Anything you buy with a real or implied warranty. Google is your friend.