Transmission control, function

Transmission control is divided into the functions of electronic transmission control (ETC) and hydraulic transmission control.

Whilst the electronic transmission control [ETC] takes over the gear selection and adaptation of pressures to the torque to be transmitted, the power supply of the transmission is controlled via the hydraulic elements of the electrohydraulic control unit. The oil supply to the hydraulic elements, such as the hydrodynamic torque converter, the shift elements and the hydraulic transmission control, is provided by way of an oil pump connected to the torque converter. The electronic transmission control (ETC) makes possible a precise adaptation of pressures to the respective operating conditions and to the engine output during the gearshift phase, resulting in a significant improvement in shift quality. It is possible to reach the engine rpm limit in the individual gears using full throttle and kickdown.

The shift range can be changed in the forwards gears while driving, however the ETC prevents an unacceptably high engine speed by means of a downshift lockout device Furthermore ETC offers the advantage of flexible adaptation to various vehicle and engine versions. The ETC [EGS] control unit (N15/3) monitors and shifts depending on:

 The vehicle speed

 The position of the selector lever

 Accelerator pedal position

 The state of the transmission

 Signals via the Controller Area Network (data bus/CAN bus) (CAN)