Note: On models equipped with traction control, the ABS unit also controls the electronic differential lock system (Electronic Differential Locking - EDL) and traction control system (Anti-Slip Regulaton - ASR).
1. The ABS system is installed on all vehicles as standard equipment. The system includes a hydraulic unit, an electronic control unit (ECU) and four wheel sensors. The hydraulic unit contains eight electromagnetic hydraulic valves (two for each brake - inlet and outlet) and an electric return pump. The purpose of the system is to prevent wheel locks during sudden braking. This is achieved by automatically releasing the brakes on the corresponding wheel, after which the braking force is applied to the wheel again. If one of the rear wheels locks, the braking force is released and applied again to both wheels simultaneously.
2. The electromagnetic valves are controlled by signals coming from the electronic control unit, which in turn is controlled by signals coming from four wheel speed sensors. The magnetic wheel speed sensors are triggered by toothed setting rings mounted on the wheel hubs. By comparing these signals, the electronic control unit can calculate the speed of the vehicle's wheels. If the speed of any wheel deviates from the vehicle's speed, by processing the signals received, the system can predict the moment when the slowing wheel will lock. Under normal conditions, the system behaves in the same way as a system without ABS.
3. If the system detects that any wheel is locked, it commands the corresponding valve in the hydraulic unit to isolate the brake of the corresponding wheel from the master cylinder.
4. If the wheel speed continues to decrease relative to the other wheels, the ABS system forces brake fluid back into the master cylinder, reducing braking. When all four wheels slow down equally, the return pump stops and all solenoids open again, allowing the master cylinder to apply hydraulic pressure to the slave cylinders again. This cycle can be repeated several times per second.
5. The action of the electromagnetic rivet and return pump creates pulsations in the hydraulic system, they are transmitted to the brake pedal and the operation of the return pump can also be heard.
6. On models with traction control, the system also performs the functions of the EDL and ASR systems. If, during acceleration, the system receives a signal about wheel slippage, it applies braking force to that wheel via the hydraulic unit until normal movement is restored.
7. The operation of the ABS system depends heavily on electrical signals. To prevent false signals from affecting the system, a built-in safety circuit monitors all signals coming into the ECU. If a false signal is received or the voltage in the network is low, the system is automatically switched off, and a warning signal about the ABS system being switched off lights up on the panel. At the same time, the normal mode of operation of the braking system is maintained.
8. Early models were equipped with the Bosch 5.0 system, with separate hydraulic and electronic units. Later systems are equipped with the Bosch A8S 5.3 systems, which have a combined electronic-hydraulic unit.
9. If a malfunction occurs in the systems, the vehicle should be presented to the dealer for diagnostics and repair.