ESC (Electronic Stability Control) System

Components and Component Location

Components

Description and Operation

ESC Description

Electronic Stability Control (ESC) detects critical driving conditions, such as panic reactions in hazardous situations, and stabilizes the vehicle by intervening individually at the wheels in the braking system and engine management.

ESC adds an additional function to ABS known as Active Yaw Control (AYC). The functions of TCS, EBD and ESC are closely related. In contrast, the ABS/TCS function controls wheel slip during braking and acceleration and thus mainly intervenes in the longitudinal dynamics of the vehicle, while Active Yaw Control stabilizes the vehicle about its vertical axis.

This is achieved by braking individual wheels and adapting the instantaneous engine torque without any action required by the driver.

ESC mainly consists of three units: sensors, electronic control unit 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 of ABS is still maintained.

ESC Control Description

The ESC system consists of the ABS/EBD, TCS and AYC functions.

ABS/EBD function: The ECU converts the active sensor signal (current switching) received from the four wheel sensors into square waves. Using the input of the above signals, the ECU calculates the vehicle speed as well as the acceleration and deceleration of each of the four wheels. The ECU then decides whether to activate ABS/EBD or not.

The TCS function prevents wheel slip in the direction of travel by adding brake pressure and reducing engine torque via the CAN bus. The TCS function uses the wheel speed sensor signal to detect wheel slip before the ABS function.

The AYC function prevents unstable vehicle maneuvering. To determine the vehicle maneuver, the AYC function uses signals from the maneuver sensors (yaw rate sensor, lateral acceleration sensor and 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 a signal to reduce engine torque.

After the ignition is turned on, the ECM continuously diagnoses system malfunctions (self-diagnosis). If a system malfunction is detected, the ECM informs the driver of the system malfunction through 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
   excessive oversteer (Front wheel outside only)	IN (NO)	OFF	OPEN
   	OUT (NC)	OFF	CLOSE

   
   

   

ABS Warning Lamp Module

The active ABS warning lamp module indicates the self-check and malfunction status of the ABS. The ABS warning lamp illuminates under the following conditions:

• 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 self-check and malfunction status of the EBD. However, if the parking brake switch is on, the EBD warning lamp is always illuminated regardless of EBD operation. The EBD warning lamp illuminates under the following conditions:

• 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.

• The cluster lamp illuminates when communication with the CAN module is not possible.

ESC Function/Warning Lamp

The ESC function/warning lamp indicates the self-check and malfunction status of the ESC system.

The ESC function/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 (other than standard mode).

• The cluster lamp illuminates when communication with the CAN module is not possible.

ESC OFF Indicator Lamp

The ESC OFF indicator lamp indicates the self-check and operating status of the ESC.

The ESC OFF indicator 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

The ESC ON/OFF switch is used to switch the ESC function between ON and OFF states based on driver actions.

The ON/OFF switch is a normally open, momentary contact switch. When the contacts are closed, the switch connects the circuit to the ignition.

The initial state of the ESC function is ON, and the switch state is also ON.