Electronic Stability Control (ESC)

The ABS module continuously monitors the vehicle motion relative to the intended course. This is done by using sensors to compare the steering wheel input and the yaw rate sensor input with the actual vehicle motion. On vehicles equipped with active park assist, the SASM sends the steering wheel angle and rate of change information to the ABS module over the HS-CAN. On vehicles without active park assist, the PSCM sends the steering wheel angle and rate of change information to the ABS module over the HS-CAN. The RCM sends the yaw rate sensor information to the ABS module over a private HS-CAN. If the ABS module determines from the inputs the vehicle is unable to travel in the intended direction, brake pressure to the appropriate brake caliper(s) or wheel cylinder(s) is modulated 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 reduce vehicle speed to help stabilize the vehicle and sends this torque reduction message to the PCM over the HS-CAN. The ABS module also sends a traction event message to the BCM over the HS-CAN, the BCM relays the traction event 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 traction event message it flashes the stability-traction control indicator (sliding car icon). Once the vehicle instability 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).

On certain vehicles equipped with a 2.0L Gasoline Turbocharged Direct Injection (GTDI) engine, the ESC system can be disabled by the driver through the ESC OFF switch. Pressing the switch once disables the traction control system and reduces the amount of ESC intervention. Pressing and holding the switch for 5 seconds disables both traction control and the ESC. The system remains in the selected state until the driver enables the systems with a single press of the ESC OFF switch or until the ignition is cycled from OFF to ON.

The ESC system does not operate with the transmission in REVERSE. The ESC system is disabled if there are any wheel speed sensor, stability sensor or steering angle sensor Diagnostic Trouble Codes (DTCs) present in the ABS module. Also, if there is a communication error between the ABS module and the SASM, the ABS module and the PSCM or the ABS module and the RCM, the ESC system is disabled. When the ESC system is disabled, due to driver selection, Diagnostic Trouble Codes (DTCs) or a loss of communication, the ABS module sends a message to the BCM which relays the message to the IPC over the MS-CAN to illuminate the stability-traction control indicator (sliding car icon).