C200SE automatic transmission delayed changing up

[D.rice]

I have a late 2020 C200SE with the mild hybrid engine. I believe I have experienced a problem with automatic transmission whereby the car fails to change up principally when going downhill. The problem is erratic but happens once or twice a day. It does not depend on whether the car is in eco or comfort mode or on the engine temperature or whether the ambient outside temperature is hot or cold. It is most easily recognised in seemingly getting stuck in first gear but the problem probably extends to 2nd and 3rd gears too. The car can get to 4500rpm or higher at which point I switch to manual. Any ideas would be gratefully received. Is this related to a problem with the energy regeneration system.
Thanks David

 

[D.rice]

After looking at the data on the car Mercedes opted to change the gearbox. The delayed changing up has disappeared and the timing of all the changes seems perfect. Also the car engages 7th and 8th gears far more frequently. I haven't yet found out what was wrong with the old box and I'm keen to know. It's hard to believe that mine is the only car with this issue....... if Mercedes ever get to the bottom of this I'll update this thread.

 

[D.rice]

The current theory is that the problem was caused by a leaking oil seal from the clutch pack in the automatic transmission.

 

[Russ A]

We have had a similar problem with our 2021 C200 9G mild hybrid petrol estate travelling long distance over the Christmas holidays. The car isn't changing into the 9th (top) gear on the motorway. You can change it up manually with the paddle and when required it is reluctant to drop down the gears
The fuel consumption seems about 10 to 15% worse on regular long runs too, which tends to say its changing up or down less efficiently
I can't talk to Mercedes currently, but it's interesting that another car has had a similar problem

 

[D.rice]

Hope you get it sorted. My car is so different now. Although the problem was most noticeable in the delayed shift from 1st to 2nd I also noticed the reluctance to change into the highest gears. In contrast changing with the paddle wheel was not a problem. It's all sorted now. As far as I am aware this is the first time has been noted for any vehicle in Sheffield. The main dealers were very helpful and thankfully Mercedes took it seriously. The problem was erratic at first but gradually over a period of 6 months git worse. Good luck.

 

[Russ A]

The problem has only been apparent for a few weeks, but obviously won't get any better. The car is now booked in at Mercedes Benz Brooklands (Owned by Mercedes) on Monday and they plan to keep it until they have resolved the problem
They were helpful on the phone and are giving us a loan car, as you would expect
I'll let you know how we get on

 

[LostKiwi]

We have had a similar problem with our 2021 C200 9G mild hybrid petrol estate travelling long distance over the Christmas holidays. The car isn't changing into the 9th (top) gear on the motorway. You can change it up manually with the paddle and when required it is reluctant to drop down the gears
The fuel consumption seems about 10 to 15% worse on regular long runs too, which tends to say its changing up or down less efficiently
I can't talk to Mercedes currently, but it's interesting that another car has had a similar problem

Have you recently had the emissions update applied?

 

[Russ A]

An interesting point, Lost Kiwi! The car hasn't been with the garage, but it does have the facility for remote software updates, so the emissions update may have been applied

 

[LostKiwi]

The emissions update has the symptoms you describe.
Worse economy, reluctant to use 9th at 70mph.

Give it a couple of tanks full and it may settle down as it readapts to your car and driving.

 

[D.rice]

Good luck. Mercedes provided me with a car for five weeks. Very nice too.

 

[Russ A]

I took the car into Mercedes at Brooklands and they had it for the day. The say they have reprogrammed and recoded the transmission control unit and this will fix things
I need to use the car for a while and also get it on a clear motorway or dual carriageway to test it properly. I can't really tell in heavy local traffic
I'll give an update when I've done that!