A trailer control valve comprises a valve electronic control port adapted to receive an electronic control signal; a valve pneumatic supply port unrestrictedly fluidly communicating with a first supply of a pneumatic fluid; a valve pneumatic control port normally proportionally fluidly communicating with a second supply of the pneumatic fluid based on a pressure representing a driver brake demand, the first supply of the pneumatic fluid being in an independent pneumatic circuit from the second supply of the pneumatic fluid; and a valve delivery port selectively fluidly communicating with at least one of the valve pneumatic supply port and the valve pneumatic control port based on the electronic control signal, the pressure representing the driver brake demand and a pressure of the first supply of the pneumatic fluid. A first pneumatic check valve includes a first check valve supply port fluidly communicating with the first supply of the pneumatic fluid; and a first check valve delivery port fluidly communicating with the relay valve pneumatic supply port. The first pneumatic check valve controls the fluid communication of the first supply of the pneumatic fluid with the relay valve pneumatic supply port based on the pressure of the first supply of the pneumatic fluid at the valve pneumatic supply port.