The system consists of a hydraulic modulator (contains electromagnetic valves and hydraulic accumulators), electric return pump, four wheel sensors (one on each wheel) and electronic control unit (ECU).
The purpose of the system is to prevent wheel locking during sudden braking. As soon as one of the wheels is close to locking, the system automatically switches off the brake unit, and when the threat of locking has passed, it switches on again. In the event of ABS failure, the braking system works as a normal system without ABS.
The electromagnetic valves that regulate the brake fluid pressure in the working cylinders are controlled by an electronic unit that receives signals from wheel speed sensors. The sensors monitor the rotation speed of each wheel. By comparing these signals, the control unit determines which wheel has slowed down and is close to locking.
The electronic control unit sends a signal to the corresponding modulator valve and the brake fluid pressure in this brake unit decreases. The hydraulic pressure in each caliper is regulated separately.
If the wheel speed continues to decrease, the ECU activates the return pump, which pumps brake fluid back into the master cylinder, reducing the pressure in the brake assembly. Once the wheel speed returns to normal, the pump is switched off, the solenoid valve opens and the braking force is applied again. This cycle can be repeated up to 10 times per second.
The operation of the electromagnetic valves and the return pump creates pulses in the hydraulic line. When the ABS system is functioning, these pulses are felt on the brake pedal.
On models with 6-cylinder engines, the hydraulic modulator is equipped with an additional set of electromagnetic valves, which are part of the traction control system (TC). The system operates at a speed of approximately 60 km / h and uses the signals provided by the wheel speed sensors. If the ECU detects that a wheel is starting to slip, the corresponding rear brake is applied for a moment.
The ABS and traction control system depend entirely on electrical signals to function properly. To prevent the system from reacting to interference, a safety circuit is built into it that monitors all pulses received by the ECU. If an extraneous signal is detected or the battery voltage is low, the systems are automatically switched off and a warning lamp on the instrument panel lights up.
Precautions
- Do not disconnect the ABS/TC electronic control unit wiring multi-connector with the ignition switch on.
- Do not use a jump starter to start the engine.
- Disconnect the ABS/TC control unit multi-pin connector before performing welding work on the vehicle.
- Do not expose the ECU to temperatures above 80°C (for example, during painting).
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