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The BMW DCT CAN protocol is not yet released, still under testings and development.

BMW DCT related links

BMW DCT Wiring information.


BMW INPA diagnostic tool.

BMW DCT error codes.

BMW DCT TCU firmware flashing.

DCT clutch relearn.

MTune - DCT Settings.

MTune - DCT Control.

DCT Realtime Data description.

DCT hardware upgrade.


Will be updated when released!




Experimental support, official support during in 2019/2020, any of the below might change during development and testings.

Note: DO NOT use this EXTRA CAN protocol on a BMW E90/E92 since it WILL interfere with stock DME CAN messages!



Required hardware and inputs


Part no


MaxxECU controlling the engine

All MaxxECUs

Preferable with E-Throttle (but works with regular wire also).

BMW M3 DCT gearbox



BMW M3 DCT gear selector



BMW M3 DCT shift knob with boot



Drivelogic button



BMW INPA or other diagnostic tool for DCT



Brake pedal/stop light active input.



Vehicle speed input (wheelspeed sensor).


Vehicle speed input is REQUIRED (preferable on UNDRIVEN WHEELS)

Any paddle shifter (which closes a circuit).


If you want paddle shifters, which you most likely want...

MaxxECU DCT cable harness.


We ONLY support this cable harness, if you make your own, you are on your own...

DCT transmission fluid

Pentosin FFL-4

Most DCT/DSG oil will most likely work...

Note: any DCT gearbox will most likely work, with their respective gear selector and buttons, but we will only support the M3 version with our DCT harness for now. Make sure the TCU firmware is correct for the connected accessories (shifter, buttons etc).

Note: We have NOT yet verified the BMW M4 gearbox (yet).



Available Real Time Data values



DCT last shift time

The last up/down shift time recorded in the system. This is not "actual shifting time", but it is the time the gearbox uses as "now I'm starting to shift" till "now I'm fully shifted". This time updates when the last shift is done.


DCT torque reduction request

When the DCT wants a torque reduction from the MaxxECU (shiftcut), there is two options for this one, see Shiftcut source in DCT Settings.


DCT Drivelogic mode

Indicates which Drivelogic mode is selected from the present drivelogic button (only available on BMW M3).


DCT sport button

Status of the BMW 135/335/Z4 SPORT button.


DCT commanded gear

The commanded gear from the shifter.


DCT engine tq

The engine Torque value sent from MaxxECU to the TCU, see DCT Control.


DCT clutch kick mode

If there is some kind of clutch kick event occurring, this will indicate its status.


DCT oil temp

The oil temp reported from the TCU.

Note: if this values is 108deg C, you have some internal TCU error code present.


DCT selector switch

Auto or Manual mode selected from the gear level.


DCT gearbox mode

If there is some kind of clutch kick event occurring, this will indicate its status.


DCT clutch kick mode

If there is some kind of clutch kick event occurring, this will indicate its status.



Will be updated when released!




Additional input

DCT clutchkick/burnout mode input. <-- Experimental usage.



Available settings/functions.

User table with custom torque value (Nm) to customize shift smoothness and also controlling the actual clutch pressures.


Throttle blip.

Time after launch torque control.

DCT clutchkick feature which disables the need for a real clutch (drifters). <-- Experimental usage.



Not working/issues/TODO

Stock BMW DCT RPM shiftpoints for now (no auto setpoints in MaxxECU). Auto mode will work to drive the vehicle moderately, manual mode is to be used for more racing oriented driving (we have no plans to update the auto mode either).

Individual clutch RPM. <-- only available with OBD instrument as of now, maybe later.

Individual clutch pressure (bar). <-- only available with OBD instrument, maybe later.

BMW M3 TCU seems to be internally limited to ~15.5bar clutch pressure, even when we report full engine torque. This will most likely only affect people in the 1000WH range anyway, we are investigating this.

Clutch relearn/adaption reset must be done using BMW tools (INPA) or other OBD tool capable of doing these functions without stock ECM present.

Downshift with throttleblip is "sometimes" little slow.

CF18 TCU error code always visible, but does not affect shifting operations.



How MaxxECU controls the BMW TCU


The BMW TCU (Transmission Control Unit) which is located on the actual gearbox itself, listens to a highly complicated CAN bus system, which we at MaxxECU have decoded and implemented as a firmware update for all MaxxECU units.


The BMW 335/M3 TCU uses CAN bus messages from the engine control unit, as well as other CAN modules found in DCT equipped BMW vehicles.

Note: Do not activate our DCT CAN protocol on your BMW vehicle....


The DCT control strategy and logic is built inside the TCU, and we "just" feed the TCU with the following data (in short, it is highly complicated):

Torque values (engine, drivers choice, vehicle, wheel, requests, max and min values).

Engine RPM.

Engine CLT.

Engine oil temperature (simulated from CLT).

Pedal position.

Required fuel amount.

E-Throttle positions (simulated from pedal positions to be able to work with non E-Throttle vehicles).

Brake pedal status.

"Vehicle speed value" to match the stock gear ratio (if using other gear ratio than the gearbox donor vehicle, we have to recalculate this value).

Traction control status.

Yaw sensor data.

Steering wheel angle position.

Wheel pressures, circumference, tolerances.

Brake pressures.

Handbrake status.

Active cruise control status.

Seat belt status.

Kombi data, odometer, MIL status.

Door and trunk status.

Ambient temperature.

Central locking status.

Ignition key/terminal status.

Gear position status.

A VERY LONG list of other status values like (vehicle speed limitations, engine speed limitations, catalyst protections, engine start torque, max values if limp home and similar values....)

Note: Some (all not listed here) are checksum verified by the TCU, and most values are 8,12 or 16-bit values).


MaxxECU distribute the following CAN messages for the DCT control:

Note: if you get weird shift operations or fault codes, please check and make sure there is no collisions on the bus you are using!



How to activate the BMW DCT protocol <-- Not officially released yet.



1. Activate the EXTRA can protocol BMW DCT. CAN Bus --> CAN settings.




2. Activate the digital input brake pedal/stop light active. Inputs --> Digital inputs.

Note: The brake switch is NEEDED for the DCT gearbox to work.




3. Mount an wheelspeed sensor, and enable it.



Important note about wheel speed

It is recommended to have at least two wheelspeed sensors mounted for best performance, if you only have 1 sensor, mount a front wheelspeed sensor.

Remember, if you go to a dyno where front wheels are not turning, and your wheel speed sensor is mounted on the wheel standing still, shift operations will not work above gear 2.

If you anyway mount a rear wheel speed sensor, during a DCT burnout automatic shift operations will occur even in manual mode.