Mespo

Good day all,

Here we had freezing temperature lately…and one day driving slowly until the motor reach normal temperature MY2018 C300
I feel something in the gas pedal / transmission and for about half a second check engine appear and disappear instantly…since then I remark that on the highway transmission do not go in 9 gear like it use to do before (around 100km)…it go to the 9 gear at 120km with high RPM.

So I look into this forum and found some interesting discussions regarding transmission relearn…which I think I will try before going to the dealership.

This is the first thread that I read :

Mercedes-Benz C-Class and C-Class AMG: How to Reset ECU and TCU | Mbworld
From the thread above…do we really need to reset ECU by disconnecting negative battery terminal?

The other threadthat I consult was this one:

W205 TCU reset - MBWorld.org Forums


From the video itself here are the instructions:

· Remove push start

· Turn the key fob to second click position

· Press accelerator to the floor wait more than 10 seconds

· Turn the key back to upright position

· Remove your foot from the gas pedal

· Wait two minutes (don’t touch any buttons or radio and so on…) and then start the car and drive it for at least 15 minutes

Does it work with 9G transmission?

Do you think I can simply follow instructions on second thread and forget about reset ECU?

Does this is safe to accomplish?

Thank you for your precious collaboration and have a great day!

Regards,

superswiss

I don't know if the procedure is still the same for the 9G, but I would suggest you first figure out why you got the CEL. The transmission may have gone into a protective mode due to whatever happened. It may come out of it by itself eventually if things continue to function normally moving forward, but at a minimum I would read out the codes to see what happened first.

Andy74

Its risky . Playing with it might end up with other issues. We are talking transmission here.

dagger22

As mentioned in an earlier post, it will be good to check what the error code is first. You can head down to a trustworthy shop to have them check for you or get a simple OBD reader pairing with a mobile app to check.

As for resetting the TCU (not ECU), the procedures are the same. This procedure is safe and you can do it regularly if you feel the trans is feeling a little lethargic.

Andy74

Did you try resetting your transmission
What was the outcome. It would be good to share.

benzdude

I have a 2015 and when the vehicle is cold (first start and drive) I get really jerky downshifts in from 5th to 4th every time. It almost feels like hard 1 sec braking.

The intensity of the jerky downshift goes away as the engine gets hotter.

I mentioned it to the service guy he said "could not reproduce" but that he upgraded the transmission software. (cannot confirm this)

The problem remains.

Mespo

Hello Andy74...for your information, I will not reset the TCU...I was only answer a question if forever reasons that the transmission act strange. But now I know that this is safe thank you dagger22!
Like I mention and like benzdude state in his reply...we add freezing temperature (-40C) with the windchill so it's normal that before everything is at nomal temperature that we experiencing this.

Keep the faith...spring is coming :-)

Thanks everyone for your precious inputs, and have a great day!

Regards,

benzdude

I just noticed another issue yesterday after driving to the store.

When I put the car in reverse it jerks forward on first press of the pedal (not smooth) and when I put it back in drive it does the same jerk motion.

What the hell is going on with my transmission? Will test more today. Maybe do another TCU reset and check again.