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Q: Transmission not shifting down while in C or S mode.

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Transmission not shifting down while in C or S mode. While in M it allows you to shift with the shifter but not whith the paddles

A: Hi, thanks for writing in. Since "manu...

Hi, thanks for writing in. Since "manual mode" bypasses all other switches (like the kick-down switch) and the "learned driving style" behavior, we know that the transmission internals (valve body, etc.) are intact. The ability to downshift with the shifter, but not the paddles (paddles work in "M" mode only for this year) is a bit confusing since both are just electronic switches. Are your paddle shifters "add-ons" (i.e. car was not initially built with paddle shift)? If so , you will need a software upgrade from Mercedes to add paddle shift functionality. A likely possibility is "learned driving style" - your prior driving did not include aggressive acceleration requiring rapid downshifting. This possibility can be overcome by disconnecting the battery for 20 minutes (or resetting with a "Star" tool if available), reconnecting the battery, followed by driving for 20-30 minutes in C and S mode, in a more aggressive manner, including rapid acceleration which invokes downshifting. The transmission controller will "learn" a more aggressive downshift profile, with the desired result. If neither of these produce the desired result, a transmission controller diagnosis with a "Star" tool is the next investment. Hope this helps and best of luck!

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