Antilock Brakes / Traction Control Systems: Description and Operation: Overview

Anti-Lock Control - Stability Assist

OVERVIEW
The ABS (anti-lock brake system) and DSC (dynamic stability control) system features a Bosch modulator, which is an integrated four-channel HCU (hydraulic control unit) and ABS (anti-lock brake system) module. The unit is located in the rear of the engine compartment on the passenger side, and is installed in the brake hydraulic circuit between the brake master cylinder and the four brake calipers.
The ABS (anti-lock brake system) module is connected to the high speed CAN (controller area network) bus, and actively interacts with other vehicle system control modules and associated sensors to receive and transmit current vehicle operating information.
When required, the ABS (anti-lock brake system) module will actively intervene and operate the HCU (hydraulic control unit) during braking or vehicle maneuvers to correct the vehicle attitude, stability, traction or speed. During incidents of vehicle correction, the ABS (anti-lock brake system) module may also request the ECM (engine control module) to control engine power in order to further stabilize and correct the vehicle.
To provide full system functionality, the ABS (anti-lock brake system) and DSC system comprises the following components:
- DSC switch.
- Four wheel speed sensors.
- Steering angle sensor.
- Yaw rate and lateral acceleration sensor.
- Stoplamp switch.
- Instrument cluster warning indicators.
- Integrated ABS (anti-lock brake system) module and HCU (hydraulic control unit).
Two variants of ABS (anti-lock brake system) module are available, Bosch ESP(R)8.1 and Bosch ESP(R)plus8.1. The Bosch ESP(R)plus8.1 system is fitted to vehicles with ACC (adaptive cruise control) and incorporates a feature known as electronic brake prefill.
Electronic brake prefill, senses any rapid throttle lift off, activating a small brake hydraulic pressure build-up of approximately 3 to 5 bar (43.5 to 72.5 lbf/in2) in anticipation of the brakes being applied. This application produces a quicker brake pedal response and consequently slightly shorter stopping distances. When the ECM (engine control module) detects rapid throttle lift off it signals the ABS (anti-lock brake system) module which controls the HCU (hydraulic control unit) to apply a low brake pressure to assist in a quicker brake application.

NOTE:
All vehicles with ACC are supported by the Bosch ESP(R)plus8.1 system.
The ABS (anti-lock brake system) provides the following brake functions that are designed to assist the vehicle or aid the driver:
- ABS (anti-lock brake system).
- DSC, including Trac DSC.
- CBC (corner brake control).
- EBD (electronic brake force distribution).
- ETC (electronic traction control).
- EBA (emergency brake assist).
- EDC (engine drag-torque control).
- EUC (enhanced understeer control).
- Electronic brake prefill (vehicles with ACC only).
All the brake functions listed are automatically active when the ignition is in power mode and the engine is running. The DSC system can be selected to off using the DSC switch.

WARNING: Although the vehicle is fitted with DSC, it remains the drivers responsibility to drive safely according to the prevailing conditions.