Vehicles equipped with automatic transmissions are normally fitted with a TCU (Transmission Control Unit). The TCU controls all aspects of the transmission’s functionality e.g. gear shift and torque limitation. The TCU works in harmony with the ECU (Engine Control Unit) by sending and receiving real time data across the vehicles network system. When tuning a vehicle, it is often recommend to have the ECU and TCU remapped simultaneously, this ensures both control units continue to work in harmony and will help to fully optimize the performance and driveability of the vehicle.