ESC (Electronic Stability Control) System

Components and Component Location

Components

1. ESC Control Module (HECU) 2. Front Wheel Speed Sensor

3. Rear Wheel Speed Sensor

Description and Operation

ESC Description

The Electronic Stability Control (ESC) system recognizes critical driving conditions, such as panic reactions in hazardous situations, and stabilizes the vehicle by individual wheel braking and intervention in engine control. ESC adds an additional function known as Active Yaw Control (AYC) to the ABS, TCS, EBD and ESC functions. 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 individual wheel braking and adaptation of instantaneous engine torque without any action required by the driver. ESC mainly consists of three components: sensors, electronic control unit and actuators. The stability control function operates in all driving modes and operating conditions. Under certain driving conditions, the ABS/TCS function may be activated simultaneously with the ESC function in response to driver commands. In the event of a stability control function failure, the basic safety function, ABS, continues to operate.

ESC System Description: The ESC system consists of 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 square waves. 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 the ABS/EBD system should be activated or not. TCS Function: The TCS function prevents wheel slip in the direction of travel by reducing brake pressure and engine torque via CAN bus. The TCS function uses the wheel speed sensor signal to detect wheel slip, in the same way as the ABS function. AYC Function: The AYC function prevents unstable vehicle maneuvering. To determine vehicle maneuvering, the AYC function uses signals from the maneuvering sensors (yaw rate sensor, lateral acceleration sensor and steering wheel angle sensor). If vehicle maneuvering is unstable (oversteer or understeer), the AYC function applies brake pressure to a specific wheel and sends an engine torque reduction signal via CAN. After the ignition is switched on, the ECU continuously diagnoses system failures (self-diagnosis). If a fault is detected in the system, 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 not operating: 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 indicates a self-check and an ABS malfunction state. 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 indicates a self-check and an EBD malfunction state. However, if the parking brake switch is ON, the EBD warning lamp is always illuminated regardless of EBD function. 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 a self-check and an ESC malfunction state. 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 Lamp: 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: The ESC ON/OFF switch is used to turn the ESC function on or off according to the driver's actions. The ESC ON/OFF switch is a normally open, momentary contact switch. When the contacts are closed, the circuit is switched to ignition. The initial state of the ESC function is ON, and the switch state is ...