Description and Operation

ESC Description

For optimum driving safety, there is now a system called ESC (Electronic Stability Control). ESC recognizes critical driving conditions, such as panic reactions in hazardous situations, and stabilizes the vehicle by individually braking the wheels and intervening in engine control. ESC adds an additional function known as Active Yaw Control (AYC) to the functions of ABS, TCS, EBD and ESC. While the ABS/TCS function controls wheel slip during braking and acceleration and thus mainly intervenes in the longitudinal dynamics of the vehicle, Active Yaw Control stabilizes the vehicle about its vertical axis. This is achieved by individually braking the wheels and adapting the instantaneous engine torque, without any action required from the driver. ESC consists mainly of three components: sensors, an electronic control unit (ECU) and actuators. The stability control function operates under all driving and operating conditions. Under certain driving conditions, the ABS/TCS function may be activated simultaneously with the ESC function in response to driver input. In the event of a failure of the stability control function, the basic safety function, ABS, continues to operate.

ESC Control Description. The ESC system includes the ABS/EBD, TCS and AYC functions. ABS/EBD function: The ECU converts the analog sensor signal (current shift) received from the four wheel sensors into a square wave. Using the input of the above signals, the ECU calculates the vehicle speed and the acceleration and deceleration of the four wheels. The ECU then determines whether or not to activate ABS/EBD. TCS function: Prevents wheel slip in the direction of travel by adding brake pressure and reducing engine torque via CAN communication. The TCS function uses the wheel speed sensor signal to determine wheel slip, together with the ABS function. AYC function: Prevents unstable vehicle maneuvering. To determine the vehicle maneuver, the AYC function uses the maneuver sensor signals (yaw rate sensor, lateral acceleration sensor, steering wheel angle sensor). If the vehicle maneuver is unstable (oversteer or understeer), the AYC function applies brake pressure to the specific wheel and sends an engine torque reduction signal via CAN. After the ignition is turned on, the ECU continuously diagnoses the system for malfunctions (self-diagnosis). If a system malfunction is detected, the ECU informs the driver of the system failure via the BRAKE/ABS/ESC warning lamp (fail-safe warning).

Input and Output Diagram

Cruise Control Operating Mode

ESC Hydraulic Circuit Diagram

1. 1
   ESC Does Not Operate: Normal Braking.

   Solenoid valve	Continuity	Valve	Motor Pump	TC Valve
   IN (NO)	OFF	OPEN	OFF	OFF
   OUT (NC)	OFF	CLOSE

2. 2
   Cruise Control Operation

   Solenoid valve		Continuity	Valve	Motor Pump	TC Valve
   Understeer (Inside Rear Wheel Only)	IN (NO)	OFF	OPEN	ON	ON
   	OUT (NC)	OFF	CLOSE
   Oversteer (Outside Front Wheel Only)	IN (NO)	OFF	OPEN
   	OUT (NC)	OFF	CLOSE

   
   

   

ABS Warning Lamp Module. The active ABS warning lamp module indicates the ABS self-check and malfunction status. The ABS warning lamp should illuminate:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• In case of ABS operation failure during braking.
• In diagnostic mode.
• When the ECU connector is disconnected from the ECU.
• The cluster lamp illuminates when communication with the CAN module is not possible.

EBD/Parking Brake Warning Lamp Module. The active EBD warning lamp module indicates the EBD self-check and malfunction status. However, if the parking brake switch is ON, the EBD warning lamp always illuminates regardless of the EBD function. The EBD warning lamp should illuminate:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• When the parking brake switch is on or the brake fluid level is low.
• When the EBD function has failed.
• In diagnostic mode.
• When the ECU connector is disconnected from the ECU.

ESC Warning Lamp (ESC System). The ESC warning lamp indicates the ESC self-check and malfunction status. The ESC warning lamp illuminates under the following conditions:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• When the ESC function is inhibited due to a system failure.
• When ESC control is operating. (Flashing - 2 Hz)
• In diagnostic mode (except standard mode).
• The cluster lamp illuminates when communication with the CAN module is not possible.

ESC OFF Lamp (ESC System). The ESC OFF lamp indicates the ESC self-check and operating status. The ESC OFF lamp operates under the following conditions:

• In initialization mode after IGN ON (continuously for 3 seconds).
• The ESC OFF lamp illuminates when the driver presses the ESC OFF button.

ESC On/Off Switch (ESC System). The ESC On/Off switch is used to switch the ESC function between ON and OFF states according to driver operation. The On/Off switch must be a normally open, momentary contact switch. Closed contacts switch the circuit to ignition. The initial state of the ESC function is ON, and the switch toggles the state.