ABS CHECK/ADJUSTMENT DEVICES

Description 3340A

DESCRIPTION OF COMPONENTS

Electro-hydraulic unit

Composition

Structure

The unit consits of an electronic control unit (1) and an electro-hydraulic control unit (2).

Electronic control unit

Specifications

Function

The electronic control unit carries out the following functions:

• acquiring the data coming from the wheel rpm sensors
• memorizing the control parameters defined during the vehicle P.D.I.
• memorizing the software
• processing the data acquired
• controlling the braking process
• detecting faults in the ABS components
• memorizing the fault codes and activating the ABS and EBD warning lights
• transmitting and receiving data via the C-CAN line
• transmitting and receiving data via the diagnostic connector

PIN OUT

1 - Power earth

2 - +30 power supply

3 - N.C.

4 - N.C.

5 - Signal earth

6 - +30 Supply

7 - N.C.

8 - N.C.

9 - N.C.

10 - N.C.

11 - K diagnostic line

12 - Left front sensor signal

13 - Left rear sensor positive

14 - Left rear sensor signal

15 - Right front sensor positive

16 - Left rear sensor signal

17 - N.C.

18 - N.C.

19 - N.C.

20 - N.C.

21 - N.C.

22 - N.C.

23 - +15 Supply

24 - CAN-H line

25 - N.C.

26 - N.C.

27 - N.C.

28 - Left front sensor positive

29 - N.C.

30 - Right rear sensor positive

31 - Right rear sensor signal

32 - N.A. stop button

33 - N.C.

34 - N.C.

35 - N.C.

36 - N.C.

37 - VSO vehicle speed (recovery)

38 - N.C.

39 - N.C.

40 - CAN-L line

41 - N.C.42 - N.C.

BASIC WIRING DIAGRAM

A - Solenoid valve relay

B - Pump motor relay

C - Pump motor

D - Valve assembly

E - Electronic control unit

FL - Left front sensor

FR - Right front sensor

RL - Left rear sensor

RR - Right rear sensor

1A-1B - Left front wheel solenoid valves

3A-3B - Right front wheel solenoid valves

4A-4B - Left rear wheel solenoid valves

2A-2B - Right rear wheel solenoid valves

Electro-hydraulic control unit

Specifications

Function

It has the task of modulating the pressure of the fluid at the brake calipers via solenoid valves with the following operating stages:

• brake fluid pressure increase
• brake fluid pressure maintenance
• brake fluid pressure discharge

Composition

Structure

the electro-hydraulic control unit is composed of:

• eight 2-way solenoid valves
• a dual circuit recovery pump
• two low pressure accumulators
• two high pressure accumulators

1 - Brake servo brake pump assembly

2 - Electro-hydraulic control unit

3 - Left rear wheel

4 - Right front wheel

5 - Left front wheel

6 - Right rear wheel

Active sensors

Specifications

System details

The adoption of active sensors offers the following advantages:

• less sensitivity to the distance between the sensor and the magnetic ring (gap)
• a reduction in sensitivity to electro-magnetic interference
• the capacity of the active sensor to measure wheel rpm speeds down to zero (instead of 2.5 km/h for passive sensors)
• a saving in weight and dimensions
• a simplification of the transmission couplings through the elimination of the flywheels.

Composition

Structure

Active sensors consist of two fundamental components:

• a multipolar magnetic codifier (1) incorporated in the wheel hub bearing
• a (magnectic-resistive) receiver (2) facing the codifier.

FRONT SENSOR

REAR SENSOR

Operation

General remarks

The active sensor operates according to the variation in the internal electrical resistance according to the intensity and direction of the lines of force of an external magnetic field (multipolr magnetic codifier) producing a variable square wave signal whose frequency varies according to the rotation speed of the wheel, but with a constant amplitude.

The active sensor is therefore an integrated electronic sensor, connected by means of a cable to the ABS control unit, from which it receives an electrical supply and to which it transmits the speed of the vehicle.

The flywheel is a multipolar ring, an elastomer with a certain quantity of magnetic particles which, by means of a special magnetization technique, are orientated to produce different magnets with alternate North South poles in a circumference arrangement.

1 - Magnetized seal

2 - Bearing

3 - Sensor head

4 - Active sensor

5 - Sealed connector