Description and Operation

ESP Description

Optimal driving safety now has a name: ESP, Electronic Stability Program. ESP recognizes critical driving conditions, such as panic reactions in dangerous situations, and stabilizes the vehicle by individually braking the wheels and intervening in engine torque without the driver needing to operate the brake or accelerator pedal. ESP adds an additional function known as Active Yaw Control (AYC) to the ABS, TCS, EBD and ESP 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 individually braking the wheels and adapting the instantaneous engine torque without any action required from the driver. ESP essentially consists of three units: sensors, electronic control unit and actuators. The stability control function operates under all driving modes and operating conditions. Under certain driving conditions, the ABS/TCS function may be activated simultaneously with the ESP function at the driver's command. In the event of a stability control function failure, the basic safety function of the ABS remains available.

ESP Control Description The ESP system includes ABS/EBD, TCS and AYC (Active Yaw Control) functions. ABS/EBD function: The ECU converts the active sensor signals (current switching) received from the four wheel sensors into a square wave form. Using the input of the above signals, the ECU calculates the vehicle speed and the acceleration and deceleration of the four wheels. The ECU determines whether the ABS/EBD system should operate or not. The TCS function prevents wheel slip in the direction of travel by reducing brake pressure and engine torque via CAN communication. The TCS function uses the wheel speed sensor signal to determine 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, steering angle sensor). If the vehicle maneuver 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 turned ON, the ECU continuously diagnoses system malfunctions (self-diagnosis). If a system malfunction is detected, the ECU informs the driver through the BRAKE/ABS/ESP warning lamp (fail-safe warning).

Input and Output Diagram

ESP Operation Mode

1. 1
   STEP 1: ESP analyzes the driver's intention.

   

2. 2
   STEP 2: It analyzes the vehicle motion with ESP.

   

3. 3
   STEP 3: The HECU calculates the required strategy, then activates the appropriate valves and sends torque control requests via CAN to maintain vehicle stability.
4. 4
   ESP not operating — normal braking.

   	Inlet Valve (IV)	Outlet Valve (OV)	Traction Control Valve (TCV)	High Pressure Switching Valve (HSV)	Return Pump
   Normal Braking	Open	Close	Open	Close	OFF

   
   

   

5. 5
   ESP Pressure Increase Mode

   	Inlet Valve (IV)	Outlet Valve (OV)	Traction Control Valve (TCV)	High Pressure Switching Valve (HSV)	Return Pump
   Normal Braking	Open	Close	Closed (Partially)	Open	ON (engine speed control)

   
   

   

6. 6
   ESP Pressure Hold Mode (controlled only for FR)

   	Inlet Valve (IV)	Outlet Valve (OV)	Traction Control Valve (TCV)	High Pressure Switching Valve (HSV)	Return Pump
   Normal Braking	Close	Close	Closed (Partially)	Open	OFF

   
   

   

7. 7
   ESP Pressure Decrease Mode (controlled only for FR)

   	Inlet Valve (IV)	Outlet Valve (OV)	Traction Control Valve (TCV)	High Pressure Switching Valve (HSV)	Return Pump
   Normal Braking	Close	Open	Closed (Partially)	Open	ON (low engine speed control)

   
   

   

   

ESP Operating Mode ABS Warning Lamp The ABS warning lamp indicates the self-diagnosis and malfunction status of the ABS system. 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.

EBD/Parking Brake Warning Lamp The EBD warning lamp indicates the self-diagnosis 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 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.

ESP Function/Warning Lamp (ESP System): The ESP function/warning lamp indicates the self-check and fault status of the ESP. The ESP function/warning lamp operates under the following conditions:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• When ESP function is suppressed due to a failure.
• In diagnostic mode.
• When the ESP system is operating (flashing - 2 Hz).

ESP OFF Lamp The ESP OFF lamp indicates the self-diagnosis and operating status of the ESP. The ESP OFF lamp illuminates under the following conditions:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• When the driver turns off the ESP function using the switch.

ESP ON/OFF Switch (ESP System)

• Stage 1: The ESP engine control function stops when the ESP OFF indicator on the instrument panel illuminates by pressing the ESP OFF button for 0.15 seconds. (Brake control function operates normally.)
• Stage 2: The ESP engine and brake control functions stop when the ESP OFF indicator on the instrument panel illuminates by pressing the ESP OFF button for 3 seconds.