Trailer vehicle and trailer control system

A method of controlling brake pressures in a trailer vehicle braking system, which braking system comprises a trailer brake module for controlling a braking force on a wheel or wheels on the trailer, which trailer brake module is adapted to receive data inputs from sensors on the trailer and a control pressure from a towing vehicle in a control line, and wherein the braking system comprises a second ECU, which second ECU is configured to receive sensor inputs from sensors on the trailer and is configured to communicate with the trailer brake module and to communicate with the towing vehicle, the method comprising:

• determining, by the second ECU, whether the control pressure should be increased or decreased;
• and
• sending, by the second ECU, a request to the towing vehicle to increase or decrease the control pressure, respectively, to modulate the pressure applied on the trailer.