Electronic Stability Control (ESC) System

The Electronic Stability Control (ESC) system is controlled by the ABS module and uses the same wheel speed sensors and tone rings that are used for the anti-lock control system. The ESC system also uses input from the steering wheel rotation sensor, the stability control sensors (yaw rate, longitudinal and lateral acceleration located in the Restraints Control Module (RCM)) and information from other modules sent over the HS-CAN to help maintain vehicle stability. The ABS module uses all of these inputs to continuously monitor the vehicle's direction of travel relative to the driver's intended course. If the ABS module determines from all these inputs that the vehicle is unable to travel in the intended direction, it modulates brake pressure to the appropriate brake caliper(s) 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 sends a message over the HS-CAN that a stability event is taking place. When the PCM receives this message, it assists with vehicle stability by adjusting engine timing and decreasing fuel injector pulses. When the IC receives this message, it flashes the stability/traction control indicator (sliding-car icon). Once the stability condition has been corrected, the ABS module returns the solenoid valves in the HCU to their normal position, deactivates the hydraulic pump motor and sends another message over the HS-CAN indicating that the event has ended. The PCM returns engine timing and fuel injectors to normal operation and the IC extinguishes the stability/traction control indicator.

If the anti-lock control system is disabled due to DTCs being present in the ABS module, the ESC system is disabled. When the ESC system is disabled due to DTCs being present, both the ABS warning indicator and the sliding-car icon are illuminated.