Skoda Felicia

since 1994 release

Repair and operation of the car

System of anti-blocking of brakes (ABS) - the general information

Components of the brake system with ABS


1 — the Control lamp of ABS 2 — the Control lamp of level of brake fluid 3 — the Hydraulic pump ABS 4 — the Hydraulic modulator 5 — the Sensor switch of stoplights 6 — Location of the diagnostic socket	7 — the Pulse disk (an alarm rotor) of the back wheel sensor 8 — the Sensor of frequency of rotation of a back wheel 9 — the Bolt 10 — the Pulse disk (an alarm rotor) of the forward wheel sensor 11 — the Sensor of frequency of rotation of a forward wheel

The function chart of the brake system with ABS


Д — the Wheel sensor TM — the Brake mechanism 1 — the Electrohydraulic valve 2 — GTTS	3 — the Pump 4 — Valves of diagonal division of contours 5 — the Tank of brake fluid 6 — ECU

Arrangement of the sensor of frequency of rotation of a forward wheel


1 — the Wheel sensor	2 — the Pulse disk (rotor)

Arrangement of the sensor of frequency of rotation of a back wheel


1 — the Brake board 2 — the Brake drum 3 — the Nave	4 — the Wheel sensor 5 — the Pulse disk (rotor)

Cars are completed with ABS of production of ITT Automotive Europe. Are included in the package: amplifier 9'', GTTs of tandem type (23.8 mm), hydraulic modulator and connecting lines. A carving for connection of hydraulic lines of the right and left wheels on assembly of the modulator various - M12x1 and M10x1 respectively.

ABS is included in a basic equipment of some models, on the others can be established in addition. Are the hydraulic modulator with the electronic control unit (ECU) established on it a part of system and four wheel sensors. The modulator is equipped with hydraulic electromagnetic valves (on two on each of brake mechanisms [one inlet and one final]) and the electrodriving pump. A problem of system is prevention of premature blocking of wheels of the car at sharp braking. These objectives are achieved due to instant modulations of pressure in hydraulic contours of brake mechanisms of wheels.

ECU which is continuously obtaining information on the speed of rotation of each of car wheels from four wheel sensors operates operation of electromagnetic valves of the modulator. Analyzing the arriving signals, ECU determines the current speed of the movement of the car and uses it as a reference point when determining the moment of the beginning of blocking of each of wheels. In normal conditions the brake system functions as the usual, not equipped ABS.

At the time of the beginning of blocking of any of wheels of ECU issues the command for operation of the corresponding final electromagnetic valve(s) of the hydraulic modulator. As a result this brake mechanism(s) is isolated from GTTs and pressure in it ceases to increase.

If the speed of rotation of this wheel (wheels) continues to decrease, the control unit issues the command for opening inlet electromagnetic the valve(s) and activates the electrodriving pump which pumps out brake fluid back in GTTs, returning freedom of rotation to the blocked wheel (ам). As soon as the speed of rotation of a wheel (wheels) rises to the acceptable value, the pump is switched-off, and the electromagnetic valve(s) reestablishes communication of a hydraulic contour of the corresponding brake mechanism(s) with GTTs. The cycle can be repeated a set of times a second, allowing to keep control over driving at sharp braking regardless of a condition of a paving.

Functioning of electromagnetic valves and the returnable pump causes pulsations in a hydraulic contour therefore pushes of a pedal of a foot brake during functioning of ABS are quite natural phenomenon and should not cause concerns.

ABS functioning completely is based on the electric signals developed by wheel sensors. In order to avoid false operations of the modulator, ECU it is equipped with the special control contour tracing all signals arriving on the block. In case of receipt of a doubtful signal, or at identification of signs of decrease in output tension of the rechargeable battery, on an instrument guard the corresponding control lamp informing the driver on ABS refusal lights up. The brake system at the same time continues to function in the usual mode, providing adequate braking of the car.

During operation of the car you watch tightness of connections of a hydraulic path and a condition of an electrical wiring. The ABS components do not need additional service.

In case of functioning violation the ABS car should be driven away on car repair shop of the company where will be made full diagnostics of system with use of the special reader and the corresponding repair.