Trailer Sway Control

WARNING: This page is about a different car, the 2014 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

Trailer sway is the undesirable yaw force a trailer can apply to the towing vehicle. Trailer sway control is a unique function of the stability control system that uses steering wheel angle information and yaw rate information to determine if a trailer sway event is taking place. The SASM sends the steering wheel angle information to the ABS module over the HS-CAN . The RCM sends yaw rate sensor and lateral accelerometer information to the ABS module over a private HS-CAN . If it is determined that a trailer sway event is taking place, the ABS module modulates brake pressure to the appropriate brake calipers by opening and closing the appropriate solenoid valves inside the HCU while the hydraulic pump motor is activated. At the same time, the ABS module calculates how much engine torque reduction is required to eliminate the trailer sway and sends this torque reduction message to the PCM over the HS-CAN . The ABS module also sends a trailer sway event message to the BCM over the HS-CAN , the BCM then relays this message to the IPC over the MS-CAN . When the PCM receives the torque reduction message, it adjusts engine timing and decreases fuel injector pulses to reduce the engine torque to the requested level. When the IPC receives the vehicle stability event message, it flashes the stability-traction control indicator (sliding car icon) and displays TRAILER SWAY, REDUCE SPEED in the message center.

Once the trailer sway has been corrected, the ABS module returns the solenoid valves in the HCU to their normal position, deactivates the hydraulic pump motor and stops sending the traction event and torque reduction messages. The PCM returns engine timing and fuel injectors to normal operation and the IPC extinguishes the stability-traction control indicator (sliding car icon) and stops displaying the trailer sway message in the message center.

Trailer sway control only activates when vehicle speed is greater than 65 km/h (40 mph). Any malfunction that disables Roll Stability Control (RSC) also disables trailer sway control. On vehicles equipped with a message center and steering wheel switches, trailer sway control can be disabled by the driver through the message center. Regardless of the chosen state (enabled or disabled) set by the driver, trailer sway control is enabled when the ignition is cycled from OFF to ON.