TonCoronel

I am experiencing some strange issues with my transmission.

In all day driving in 'C' all is good, when in 'S' all is good but sometimes when flooring it it shifts much to soon. When in 'M' at first all is fine but after a while the real problems start. It starts to up-shift automaticly during acceleration at around 2500RPM. So when trying to accelerate out of a corner from second it jumps quickly to third, fourth etc everytime around 2500RPM. I did some testing yesterday and as soon as the troubles start in 'M' mode I cannot use the shifter pedals anymore in 'C' or 'S' mode, it briefly shows the gear I want to go into but then goes back to C or S without changing gear.
I also did a quick acceleration in first in 'M' from stand-still and then it got stuck in first untill I switches back to 'C' mode.
Now it does not go into any limp mode because when changing back to 'C' and drive normal there are no issues anymore. Also when leaving the car for the night the next morning 'M' mode is working correctly again for the first few miles and only then starting to act up again.

I had this behaviour occuring sometimes in the past and theirfore had the oil and filter replaced at 50.000 KM, I am now at around 55.000KM but it seems to get worse.

I understand then I should go to the dealer but maybe someone has already got a clue on what is going on, seems heat related to me because it only happens when driving for a while?

AMGFTW

Try a battery reset. Pull the negative terminal on your battery for more than 10 minutes.

See if that will reset the trans adaptations.

TonCoronel

Thanks but already tried that but didnt seem to work...

Any other idea?

cptdaz

Check tranny and diff fluid?

Merc63

Could the tranny be heating up too much??

Have you got the fluid and filter in the tranny flushed. You are supposed to at 50k km...

Id say your best bet is to bring it to the dealer, you should have warranty still? It might be throwing codes and not producing a CEL.

Sheep

Try to reset the ECU/TCU:

1, take off the keyless go button if you have it.
2, use the key and turn it into the second position, the dash should light up and electronics should have power.
3, with out touching the brakes, floor your accelerator and hold it for at least 10 seconds.
4, while holding down the accelerator, turn the car off.
5, wait at least 2 minutes before starting up the car again. This should reset the adaptive shifting from the ECU/TCU back to default.

If you still have problem after this, then I strongly suggest you take it to the dealer for a full check up. Good luck.

Sheep

AMGFTW

Sheep the sneeky ecu/tcu reset does not work with our cars. To my knowledge it only works on 5spd auto cars.

Sheep

Maybe, but it won't hurt to try. I did it with mine and it seemed to have worked.

Sheep

sighting

Not sure if it works on a 09, but it absolutely works on a 2010,2011

TonCoronel

Any way to do this yourself?


Yeah tranny was flushed at 50k km and filter was replaced. I am bringing it to someone that can read-out the car before bringing it to the dealer. Its a 2008 C63 so no warrently anymore, am afraid it will cost me an arm and leg if letter the dealer find out what is wrong.

I did try the TCU reset procedure some while ago but I will give it another try.

TonCoronel

I used an ELM327 bluetooth dongle with my Android phone to scan the car, it gave one error : "P374A - Drivetrain", cant find any information on the internet regarding this code. I have just cleared the code, removed battery for 1 hour and did the ECU/TCU reset, lets see if it helps.

TonCoronel

Just did a test drive but problem still there even with cold engine/transmission. Also instantly generated the p374a code...

jvanbrecht

Don't just reset the codes.. talk to you dealer, at a minimum call the SA and ask what the code means.. arbitrarily clearing the code is just asking for trouble.

TonCoronel

Your right but I was hoping it was a code that was thrown when I had the oil changed in the transmission and maybe it needed to be reset before the transmission would work normally again.

After a bit of driving there were 3 more errors logged
P0E66
P23D0
P0686
All reported under powertrain/drivetrain.

Taking it to a specialist next week...

izzyAMG

Oh no... its the end for you, just take it and fix it.

TonCoronel

Well my problems are solved! Had the car diagnosed with Xentry and it didnt show any errors on the gearbox but it did show an error with the 'Up' shifter paddle of my steering wheel.
When testing the paddle shifter with Xentry it showed that sometimes when pressing the paddle no input was received and sometimes it hang.
We disconnected the paddle and now all is fine! Fortunatly no damaged gearbox or anything like that