Kia Optima: Brake System / ESC (Electronic Stability Control) System

Components and components location

Description and operation

Electronic Stability Control (ESC) recognizes critical driving conditions, such as panic reactions in dangerous situations, and stabilizes the vehicle by individual wheel braking and engine control input.

ESC adds an additional function known as Active Yaw Control (AYC) to the ABS, TCS, EBD and ESC functions. On contrary, the ABS/TCS function controls wheel slip during braking and accelerating, and thus, mainly intervenes in the longitudinal dynamics of the vehicle, and the active yaw control stabilizes the vehicle on the vertical axis.

This is achieved by individual wheel brake intervention and adaptation of momentary engine torque with no need for any action to be taken by the driver.

ESC essentially consists of three assemblies : the sensors, the electronic control unit and the actuators.

The stability control feature works under all driving and operating conditions. Under certain driving conditions, the ABS/TCS function can be activated simultaneously with the ESC function in response to a command by the driver.

In the event of a failure of the stability control function, the basic safety function, ABS, is still maintained.

Description of ESC Control

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

ABS/EBD function : The ECU changes the active sensor signal (current shift) coming from the four wheel sensors into square waves. By using the input of above signals, the ECU calculates the vehicle speed and the acceleration & deceleration of the four wheels. And, the ECU judges whether the ABS/EBD should be actuated or not.

TCS function prevents the wheel slip of drive direction by adding the brake pressure and engine torque reduction via CAN communication. TCS function uses the wheel speed sensor signal to determine the wheel slip as far as ABS function.

AYC function prevents unstable maneuver of the vehicle. To determine the vehicle maneuver, AYC function uses the maneuver sensor signals (Yaw Rate Sensor, Lateral Acceleration Sensor, and Steering Wheel Angle Sensor).

If vehicle maneuver is unstable (Over Steer or Under Steer), AYC function applies the brake pressure on certain wheel, and sends engine torque reduction signal by CAN.

After the key-on, the ECU continuously diagnoses the system failure (self-diagnosis). If the system failure is detected, the ECU informs driver of the system failure through the BRAKE/ABS/ESC warning lamp (fail-safe warning).

Input and Output Diagram

Warning Lamp Control

ABS Warning Lamp module

The active ABS warning lamp module indicates the self-test and failure status of the ABS. The ABS warning lamp is turned on under the following conditions:

EBD/Parking Brake Warning Lamp Module

The active EBD warning lamp module indicates the self-test and failure status of the EBD. However, in case the Parking Brake Switch is turned on, the EBD warning lamp is always turned on regardless of EBD functions. The EBD warning lamp is turned on under the following conditions:

ESC Function/Warning Lamp

The ESC function/warning lamp indicates the self-test and failure status of the ESC.

The ESC function/warning lamp is turned on under the following conditions:

ESC Off Lamp

The ESC Off lamp indicates the self-test and operating status of the ESC.

The ESC Off lamp operates under the following conditions :

ESC On/Off Switch

The ESC On/Off Switch is used to toggle the ESC function between On/Off states based upon driver input.

The On/Off switch is a normally open, is a momentary contact switch.

Initial status of the ESC function is ON.

Schematic diagrams

[EPB None Apply]

[EPB Apply]

[EPB None Apply]

[EPB Apply]

Troubleshooting

Failure Diagnosis

Memory of Fail Code

Failure Checkup

Countermeasures in Fail

Warning Lamp ON

• ESC Control Module
• ESC OFF Switch
• Front Wheel Speed Sensor
• Rear Wheel Speed Sensor
• Emergency Signal System