WARNINGS: Attempts to independently interfere with the operation of electronic braking control systems will lead to their failure.
All maintenance and repair work on these systems should be carried out only at specialized service stations that have the necessary equipment and qualified personnel.
Electronic systems improve the car's handling and braking qualities, but do not replace the driver, as they cannot independently prevent incidents due to careless driving. Do not make serious mistakes in driving a car, relying on auxiliary systems.
The ABS system is used to regulate the pressure in the brake mechanisms of all wheels when braking in difficult road conditions, which prevents the wheels from locking.
The ABS system provides the following benefits:
– avoiding obstacles with a higher degree of safety, including during emergency braking;
– reduction of the braking distance during emergency braking while maintaining the directional stability and controllability of the vehicle, including when turning.
The ABS system includes:
– a hydroelectronic control unit (HECU) that receives information about the vehicle"s speed, direction of travel, and road conditions from the wheel speed sensors. After the ignition is turned on, the ABS module supplies voltage to the sensors;
WARNING: If air gets into the hydraulic electronic unit, it is impossible to bleed it without special equipment. In this regard, contact a service station to replace the unit.
– wheel speed sensors. The sensors use the Hall effect, they generate an output signal in the form of electrical pulses. The signal changes proportionally to the rotation frequency of the sensor's pulse ring, built into the front hub bearing seal and directly into the rear hub. Wheel speed information is used to determine the vehicle's speed;
– Anti-lock brake system malfunction indicator lamp (with yellow filter). The lamp lights up when the ignition is on for 3 seconds. When the starter is on, the lamp lights up continuously.
After starting the engine, it should go out immediately. If the system fails, the lamp remains lit continuously.
WARNING: If the light comes on while driving, contact a service center, as braking in all cases will occur without the involvement of the anti-lock braking system.
Based on the information received from the sensors, the ECU determines the optimal wheel braking mode.
The following operating modes of the anti-lock braking system are distinguished:
– normal braking mode. During normal braking, the electromagnetic valve is de-energized, the inlet valve is open, and the outlet valve is closed. When the brake pedal is pressed, brake fluid under pressure is supplied to the working cylinder through the electromagnetic valve and activates the wheel brake mechanisms. When the brake pedal is released, the brake fluid returns to the main brake cylinder through the inlet and check valves;
– emergency braking mode. If the wheel starts to lock during emergency braking, the ECU issues a command to the electromagnetic valve to reduce the supply of brake fluid, then voltage is supplied to each electromagnetic valve. The inlet valve closes, and the supply of brake fluid from the master cylinder is blocked; the outlet valve opens and brake fluid flows from the slave cylinder to the master cylinder and then to the reservoir, causing a decrease in pressure;
– pressure maintenance mode. When the pressure in the working cylinder drops to the maximum, the ECU issues a command to the electromagnetic valve to maintain the brake fluid pressure, voltage is supplied to the input valve and is not supplied to the output valve. In this case, the input and output valves are closed and the brake fluid does not leave the working cylinder;
– pressure increase mode. If the ECU determines that the wheel is not locked, it de-energizes the electromagnetic valve. Voltage is not supplied to the electromagnetic valves, the brake fluid enters the working cylinder through the inlet valve, the pressure in which increases.
Special equipment and tooling are required to diagnose and repair the anti-lock braking system. Therefore, if it fails, contact a specialized service station.