ABS hydraulic module: it consists of an electric pump and a hydraulic distribution box with electromagnetic valves. When you press the brake pedal, the brake pistons in the master cylinder squeeze the brake fluid through the hydraulic distribution box to the wheels. In doing so, the hydraulic distribution box regulates the brake pressure in the brake pipes that connect each front wheel to the diagonally opposite rear wheel. When the ABS starts working, the control unit sends a signal to "reduce the brake pressure". The brake fluid flows from the hydraulic distribution box back to the expansion tank. If the brake pressure increases again, the brake fluid flows from the expansion tank through the hydraulic pump directly into the corresponding brake circuit. You can notice the pump working by a slight pulsation in the brake pedal.
ABS braking system: 1 - ABS hydraulic module; 2 - rear wheel sensor; 3 - front wheel sensor.
Wheel speed sensor: rigidly connected to the wheel hub at a small distance from the toothed disk (pulse wheel). The active wheel with its toothed elevations rotates depending on the rotation of the wheel (speed) past the sensor faster or slower. Each tooth of the pulse wheel induces a short voltage surge. As a result, an alternating voltage arises in the sensor, which changes its frequency depending on the rotation speed of the wheel. The sensors measure the rotation speed of each wheel and transmit this information in the form of electrical signals to the control unit.
Each wheel is measured separately: the wheel speed sensors do not miss a single revolution. Based on the different clock frequencies of the speed sensors in the wheel turning zone, the ESP module draws a digital picture of the turning trajectory
ESP module: the ESP module is located in the Focus on the ABS module type Mk20E-1 with TCS. The distribution hydraulic box has two additional valves, with the help of which the rear wheels can be braked separately. The ESP module is in constant contact with the PCM via the SCP data collection bus.
ESP module: 1 - flange-mounted electronic module; 2 - distribution hydraulic box; 3 - electric motor with high-pressure pump.
Longitudinal acceleration sensor: consists of two pendulum switches, which are installed under the center console. During normal driving, during light acceleration or deceleration, they are in a resting state. If the deceleration or acceleration parameters programmed in the control unit are exceeded, the sensors transmit a corresponding signal to the control unit.
Malfunctions of the ABS braking system: when the ignition is on, the ABS brake system indicator light comes on. When the engine is running, it goes out within 2 seconds. If it comes on while driving, there is a fault in the system. However, in most cases you can continue driving - although without a functioning ABS. To check the system, find a Ford workshop as soon as possible. In any case, as an ABS amateur, you can check the correctness of the connectors on the control unit, on the relay, on the wheel sensors and on the hydraulic module.