Hill Start Assist

The ABS module uses the brake pedal switch message and ABS wheel speed sensor input to determine that the vehicle is at a complete stop. The transmission selector lever message and parking brake message let the ABS module know that the vehicle is not being parked. The stability sensor messages from the RCM enable the ABS module to determine if the vehicle is on an incline greater than 5 degrees or greater than a 3% grade. The hill start assist function automatically engages once the above conditions have been met. As the driver releases the brake pedal, the ABS module commands the HCU to close the isolation valves which will maintain the current brake system pressure, preventing the vehicle from rolling down the incline. The ABS will hold the brake pressure for up to 2 seconds while the driver transitions to the accelerator pedal. As the accelerator pedal is pressed and the engine RPM increases, the ABS module gradually releases the brake pressure to make sure the vehicle is neither rolling back nor driving off until there is sufficient driving torque to accelerate the vehicle forward (or backward if reversing up the incline).