SsangYong Actyon Sports II. Manual - part 153

11-7

4890-10

HECU (Hydraulic & Electronic Control Unit)

▶

to FL wheel

to RR wheel

to RL wheel

to FR wheel

Hydraulic & Electronic Control Unit (HECU)

1.

to master cylinder

11-8

1. OVERVIEW

The ESP (Electronic Stability Program) has been developed to help a driver avoid danger of losing 

control of the vehicle stability due to understeer or oversteer during cornering. The yaw rate sensor, 

lateral sensor and longitudinal sensor in the sensor cluster and the steering wheel angle sensor under 

the steering column detect the vehicle conditions when the inner or outer wheels are spinning during 

oversteer, understeer or cornering. The ESP ECU controls against oversteer or understeer during 

cornering by controlling the vehicle stability using input values from these sensors and applying the 

braking force to the corresponding wheels independently. The system also controls the engine power 

right before the wheel spin synchronized to decelerate the vehicle automatically in order to maintain the 

vehicle stable during cornering.

11-9

4890-10

ESP OFF switch

Located on the left side of 
instrument panel.

Rear wheel speed sensor

Located on the both ends of 
rear axle.

Front wheel speed sensor

Located on the hub assembly.

Sensor cluster

Located at the bottom of center 
fascia panel.

Steering wheel angle sensor

Located on column shaft with 
contact coil.

HECU assembly

Located near the brake booster 
in engine compartment and 
contains the pressure sensor.

2. COMPONENTS

11-10

3. FUNCTION

1) Term Definition

ABS: Anti-Lock Brake System

▶

When the brake pedal is abruptly depressed, the HECU calculates the slip ratio of each wheel based on 

information received from the wheel speed sensors and controls the hydraulic module data quickly and 

precisely in order to maintain the friction between the road surface and tire optimal (static friction). 

Therefore, by keeping the friction between the road surface and tire optimal, it is possible to obtain 

following effects: Enhanced steering stability, improved direction stability, reduced stopping distance and 

etc.

EBD: Electronic brake-Force Distribution

▶

This is to detect the tire speed from the wheel speed sensor in order to supply the braking pressure to 

the rear tires individually. In other words, the HECU measures the tire deceleration speed continuously 

and controls the rear inlet valve on the hydraulic modulator to obtain optimal braking force as much as 

possible. Thereby, stopping distance, braking effect and straight stability are improved.

ESP: Electronic Stability Program 

▶

This is used to make the vehicle stabilized to recognize the emergency driving conditions, and to control 

the brake for each wheels and the engine power when the brake system or acceleration will not work 

any more in dangerous circumstances. 

TCS: Traction Control System 

▶

When the wheel is slipping due to an excessive engine torque while starting off or driving, this controls 

the driving force (braking force + engine torque) in order to prevent the wheel from slipping through the 

engine or brake control. 

AYC: Active Yaw Control

▶

This has been developed to help a driver avoid danger of losing control of the vehicle stability due to 

understeer or oversteer during cornering, which is a part of the ESP function. 

HBA: Hydraulic Brake Assistant

▶

Developed based on the fact that elderly drivers depress the brake pedal too soft even when hard 

braking is necessary, this an assist system to operate the HECU drive motor immediately and apply high 

braking force to the wheels when the brake pedal is depressed softly and the vehicle should be braked 

in emergency.

ARP: Active Rollover Protection

▶

This is a supplementary device for safety in ESP system and can help minimize the rollover accidents by 

detecting a potential rollover situation through the brake and engine control when making sudden lane 

change or turning sharply by adding only the software, without any separate device or switch.