Description and Operation

ESC Description

The Electronic Stability Control (ESC) system recognizes critical driving conditions, such as panic reactions in dangerous situations, and stabilizes the vehicle by performing individual wheel braking and engine torque intervention. ESC adds an additional function called Active Yaw Control (AYC) to the ABS, TCS, EBD and ESC functions. 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 individual wheel brake action and adaptation of instantaneous engine torque without driver action. The ESC consists mainly of three units: sensors, an electronic control unit and actuators. The stability control system operates under all driving and road conditions. Under certain driving conditions, the ABS/TCS function can be activated simultaneously with the ESC function in response to driver input. If the stability control function fails, the basic safety function, ABS, is maintained.

ESC Operation Description. The ESC system includes ABS/EBD, TCS and AYC functions. ABS/EBD function: The ECU monitors the active signal (current offset) from the four square-wave wheel sensors. Based on the signal input, the ECU calculates vehicle speed, acceleration and deceleration from the four wheels. The ECU determines whether to activate ABS/EBD or not. TCS function: Prevents wheel slip by reducing brake pressure and engine torque via CAN communication. The TCS function uses the wheel speed sensor signal to detect wheel slip, in the same way as the ABS function. AYC function: Prevents unstable vehicle motion. To determine vehicle maneuvering, the AYC function uses signals from sensors (yaw rate sensor, lateral acceleration sensor, steering wheel angle). If vehicle maneuvering is unstable (oversteer and understeer), the AYC function applies brake pressure to a specific wheel and sends a signal to reduce engine torque via CAN. After ignition ON, the ECU continuously checks for system malfunctions (self-diagnosis). If a malfunction is detected in the system, the ECU (Electronic Control Unit) informs the driver using the BRAKE/ABS/ESC warning lamp. (Fail-safe)

Input and Output Diagram

ESP OPERATION MODE

ESP HYDRAULIC SYSTEM DIAGRAM

1. 1
   ESP not active: normal braking

   Solenoid valve	Continuity	Valve	Motor pump	CT valve
   IN (NO)	OFF	Open	OFF	OFF
   OUT (NC)	OFF	Closed

2. 2
   ESP Operation

   Solenoid valve		Continuity	Valve	Motor pump	CT valve
   Understeer (Inside Rear Wheel Only)	IN (NO)	OFF	Open	WE	WE
   	OUT (NC)	OFF	Closed
   Oversteer (Outside Front Wheel Only)	IN (NO)	OFF	Open
   	OUT (NC)	OFF	Closed

   
   

   

ABS WARNING LAMP MODULE. The ABS warning lamp indicates ABS self-check and malfunction status. ABS warning lamp ON:

• During the initialization phase after ALL ON (continuously for 3 seconds).
• When ABS functions related to a fault are deactivated.
• In diagnostic mode.
• When the ECU connector is disconnected from the ECU.
• The instrument cluster indicator illuminates when communication with the CAN module is not possible.

EBD WARNING LAMP / PARKING BRAKE MODULE. The active ABS warning lamp module indicates ABS self-check and ABS malfunction status. However, if the parking brake switch is activated, the EBD warning lamp will illuminate regardless of the current EBD function. The EBD warning lamp must illuminate:

• During the initialization phase after ALL ON (continuously for 3 seconds).
• When the parking brake switch is ON or when the brake fluid level is low.
• When the EBD function is faulty.
• In diagnostic mode.
• When the ECU connector is disconnected from the ECU.
• The instrument cluster indicator illuminates when communication with the CAN module is not possible.

ESP Function / Warning Lamp (ESP System). The ESP warning/function lamp indicates ESP self-check and operating status. The ESP function lamp illuminates in the following cases:

• During the initialization phase after ALL ON (continuously for 3 seconds).
• When the ESP function is prohibited due to a system failure.
• When the ESP system is operating (flashes at 2 Hz).
• In diagnostic mode (except standard mode).
• The instrument cluster indicator illuminates when communication with the CAN module is not possible.

ESP OFF Warning Lamp (ESP System). The ESP OFF lamp indicates ESP self-check and operating status. The ESP OFF lamp illuminates in the following cases:

• In initialization mode after ALL ON (continuously for 3 seconds).
• The ESP OFF warning lamp illuminates when the driver activates the ESP OFF switch.

ESP ON/OFF Switch (ESP System). The ESP ON/OFF switch is used to turn the ESP function on or off according to driver input. The ON/OFF switch must be normally open; the contact switch clicks. When the ignition switch activates the circuit, the initial state of the ESP function is activated and the switch toggles the state.