The transmission control unit (TCU) is an essential component of an electronic control unit that is responsible for controlling the transmission in a vehicle. It receives input from various sensors in the vehicle, such as the engine speed sensor and the vehicle speed sensor, and uses the information to determine the appropriate gear ratio for the transmission.
The TCU then sends signals to the transmission to engage or disengage certain gears, allowing the transmission to shift seamlessly between gears as the vehicle accelerates or decelerates.