Roll Stability Control (RSC)™

The ABS module continuously monitors the vehicle motion relative to the intended course. This is done by using sensors to compare the wheel speed sensor input, throttle position input, steering wheel input and the roll rate sensor input with the actual vehicle motion. Steering wheel angle information is calculated by the PSCM and is sent to the ABS module over the HS-CAN. Vehicle roll rate information is sent to the ABS module from the RCM over a private HS-CAN. The PCM sends the throttle position sensor information to the ABS module over the HS-CAN. The wheel speed sensor information comes directly from the ABS wheel speed sensors.

If the ABS module determines the vehicle is becoming unstable based on information from the various inputs, 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 sends a vehicle stability event message over the HS-CAN. When the PCM receives this message, it assists with vehicle stability control by adjusting engine timing and decreasing fuel injector pulses. When the IPC receives this message, it flashes the stability-traction control indicator (sliding car icon). By adjusting brake and engine torque the system can reduce the cornering forces and, therefore, the total roll movement acting on the vehicle. 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 sends another message over the HS-CAN bus indicating the stability event has ended. The PCM returns engine timing and fuel injectors to normal operation and the IPC extinguishes the stability-traction control indicator (sliding car icon).

The RSC ® function does not operate with the transmission in REVERSE. The ABS module disables the RSC ® function if there are any wheel speed sensor, stability sensor or steering angle sensor DTCs present in the ABS module. Also, if there is a communication error between the ABS module and the PSCM, PCM or the RCM, the RSC ® function is disabled. When the RSC ® function is disabled, the ABS module sends a message over the HS-CAN to the IPC to illuminate the stability-traction control indicator (sliding car icon).

The traction control, ESC and RSC ® systems can be disabled by the driver through the use of the stability-traction control switch. When the switch is pressed, a ground signal is sent to the IPC, the IPC sends a message to the ABS module via the HS-CAN. The ABS module modifies how it responds to stability control or traction control events. The system remains disabled or modified until the driver activates the function or until the ignition is cycled from OFF to ON. The stability control and traction control systems are controlled by the stability-traction control switch in the following manner:

• Momentarily pressing the switch disables the traction control system, increases the threshold for ESC intervention and does not affect the RSC ® system.
• Pressing the switch and holding it pressed for more than 5 seconds with vehicle speed under 56 km/h (35 mph) disables all 3 systems; traction control, ESC and RSC ®.
• When vehicle speed exceeds 56 km/h (35 mph) after the switch was pressed and held for more than 5 seconds, the RSC ® systems becomes enabled, the ESC becomes enabled with an increased threshold for intervention and the traction control system remains disabled.
• Pressing the switch after one or more systems have been disabled enables all 3 systems.
• Switching the transfer case to 4WD Low Locked disables all 3 systems; traction control, ESC and RSC ®.