since 2000 of release

Repair and car operation

+ 1.1. Short acquaintance to the car
+ 2. Engines A3E, A5D
+ 3. Greasing system
+ 4. Cooling system
+ 5. Fuel system
+ 6. Ignition system
+ 7. Coupling
+ 8. Transmission
+ 9. Axes and power shafts
+ 10. Suspension bracket
+ 11. Wheels and tires
+ 12. Steering
- 13. Brake system
   13.1. Specifications
   13.2. Check of the vacuum amplifier of brakes with use of devices
   13.3. Unilateral vacuum valve
   13.4. Vacuum amplifier of brakes
   13.5. Pumping of hydraulic system of a drive of brakes
   13.6. Check of brake tubes
   13.7. Check and replacement of brake hoses
   + 13.8. Brake pedal
   13.9. Replacement of forward brake shoes
   13.10. Replacement of brake shoes on back drum-type brakes
   13.11. Repair of a support of a forward brake
   13.12. Repair of the working brake cylinder
   13.13. Main brake cylinder
   13.14. Pressure limiter
   13.15. Parking brake
   13.16. ABS control unit
   13.17. Block of hydraulic management (HCU)
   13.18. Forward sensor of frequency of rotation of a wheel
   13.19. Back sensor of frequency of rotation of a wheel
   + 13.20. Gear rotor of the sensor of frequency of rotation of a wheel
   13.21. Main survey
   13.22. Check of functionality
+ 14. Body
+ 15. Air central air
+ 16. Electric equipment

13.16. ABS control unit


Arrangement of elements of brake system with ABS on the car

1–tube of the highway of a high pressure of brake system;
2–brake pedal;
3–main brake cylinder;
4–popolnitelny tank;
5–vacuum amplifier of brakes;
6–block of hydraulic management (HCU);
7–forward disk brake mechanism;
9–back drum-type brake mechanism;
10-lever of the parking brake;
11-cable of the parking brake.

The ABS control unit carries out the following functions:

      – ABS operates;
      – calculates speed of the car;
      – carries out system self-diagnostics: codes of malfunctions with self-diagnostic and safety functions are brought in memory by two separated microprocessors.

The ABS control unit continuously checks blocking of each wheel and operates each valve to regulate pressure of brake liquid if it is required.

The ABS control unit also checks that components work properly and switches off ABS at detection of failures.
Then the brake system works as standard brake system.

Sensor of frequency of rotation

The sensor of frequency of rotation finds rotation of a wheel and consists of a constant magnet and the coil. Sensors of forward wheels receive information from the gear rotors located on power shafts.

When passing teeths of a rotor about the sensor, the magnetic field of the sensor therefore the tension impulse is developed changes.

This tension is proportional to frequency of rotation of a wheel and can be measured.

Control lamps of ABS and EBD are located in a combination of devices.

Control lamp of ABS:

1) Burns during 3 with the ambassador of inclusion of ignition then dies away.
2) Dies away at engine start-up.
3) If the lamp burns constantly, means in ABS there are violations.
4) The lamp burns during self-diagnostics.
5) If the control lamp lights up periodically, means in ABS there are violations and work of systems of the car is carried out thus as though in the car there are no ABS and TCS systems.
6) The lamp burns at a detachment of the electric socket from the ECU control unit.

Control lamp of EBD (electronic distribution of force of braking):

1) Burns after ignition inclusion.
2) Dies away at engine start-up.
3) Burns at a tightening of the lever of the parking brake.
4) Burns at low level of brake liquid.
5) Burns, if electronic distribution of force of braking of EBD does not work:
      – at malfunction in the electromagnetic valve;
      – at malfunction more than in one sensor;
      – at malfunction of the ECU control unit;
      – at an overvoltage.

Block of hydraulic management (HCU)

The block of hydraulic management (HCU) consists of the pump with an electric motor and the block of valves to operate pressure of ABS.

The sensor is located in the electric motor of the pump and transmits a target signal to the ABS block which defines operability of the pump.

Diameter of an opening of a pipe of supply of brake liquid of a forward brake: 4,8 mm
Diameter of an opening of a pipe of supply of brake liquid of a back brake: 4,8 mm

The pump with two contours provides demanded pressure, and the block of valves distributes the pressure transferred to wheel brake mechanisms.

And – the forward right inlet valve;
In – the back left inlet valve;
With – the back right inlet valve;
D–forward left inlet valve;
E–forward right final valve;
F–back left final valve;
G–back right final valve;
H–forward left final valve;
M–+ engine;
N–engine (GND).

ABS self-diagnostics

The ABS control unit starts to carry out self-diagnostic functions after ignition inclusion. The ABS control unit finds malfunction for each contour and a component, comparing a system condition to a limited set of conditions in the ABS control unit. The ABS control unit stores a code of malfunction and then deduces on the diagnostic device in the form of the codes designated by four figures.

Check of codes of self-diagnostics

1. Turn a key in the ignition lock in the situation OFF and connect the diagnostic device to the diagnostic socket located about the vacuum amplifier in a motor compartment.
2. Turn a key in the ignition lock in the situation ON and on the device set model of the car and model of the diagnostic device.
3. Choose the checked parameter after block initialization.
4. Press check of codes No. 1 and find out, whether malfunction is written down.


Malfunction code – number with four figures which appears continuously while the code of malfunction is not erased by the diagnostic device.

5. According to the list of codes of malfunction reveal a faulty element and restore its working capacity.
6. After deleting of codes of malfunction from memory of the ABS control unit choose inspection point No. 4.