312000717 - 3340A ABS CHECK/ADJUSTMENT DEVICES

DESCRIPTION OF COMPONENTS

Electrohydraulic unit

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

The electronic control unit carries out the following functions:

  • acquiring the data coming from the wheel rpm sensors,
  • memorising 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.
ABS control unit pin out
PinFunction
1+ 30
2n.c.
3n.c.
4n.c.
5n.c.
6Right-hand front wheel sensor signal K071
7n.c.
8n.c.
9n.c.
10n.c.
11n.c.
12n.c.
13Earth
14C CAN ( L )
15C CAN ( L )
16Vehicle speed signal (n.c.)
17K line (n.c.)
18Right-hand front wheel sensor power supply K071
19Right-hand rear wheel sensor power supply K076
20Left-hand rear wheel sensor signal K075
21n.c.
22Left-hand front wheel sensor signal K070
23n.c.
24n.c.
25+ 30
26C CAN ( H )
27C CAN ( H )
28n.c.
29n.c.
30n.c.
31Right-hand rear wheel sensor signal K076
32+ 15
33Left-hand rear wheel sensor power supply K075
34Left-hand front wheel sensor power supply K070
35n.c.
36n.c.
37n.c.
38Earth
Hydraulic control unit

It performs the function of modulating the pressure of the fluid at the brake callipers via solenoids, with the following operating stages:

  • brake fluid pressure increase,
  • brake fluid pressure maintenance,
  • brake fluid pressure decrease.
For more details see:    See descriptions 3340 ANTI-LOCK BRAKING SYSTEM (ABS)

The hydraulic control unit consists of:

  • eight 2-way solenoid valves,
  • a dual circuit scavenging pump,
  • two low pressure accumulators,
  • two high pressure accumulators.
1. Brake servo brake pump assembly2. Hydraulic control unit3. Left rear wheel4. Right front wheel5. Left front wheel6. Right rear wheel

Active sensors

Specifications

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 size,
  • a simplification of the transmission couplings through the elimination of the phonic wheels.
Structure

Active sensors consist of two fundamental components:

  • a multipolar magnetic coding device (1) incorporated in the wheel hub bearing
  • a Hall effect receiver (2) that faces the coding device.
The active sensor functions on the basis of variation in the internal electrical resistance, according to the intensity and direction of the lines of force of an external magnetic field (multipolar magnetic coding device). It produces a variable square wave signal whose frequency varies according to the rotation speed of the wheel, but has a constant amplitude.
1. Magnetised sealing ring2. Bearing3. Sensor head4. Active sensor5. Sealed connectorThe active sensor is therefore a proximity sensor with built-in electronic system, 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 phonic wheel is a multipolar ring, an elastomer with a certain amount of magnetic particles which are aligned to form different magnets with alternating North / South polarity in a circumferential arrangement by means of a special magnetisation technique. 48 negative poles and 48 positive poles are present in total.
1. Receiver2. Hall sensor3. Sensitive elements4. Multipolar magnetic codifier5. ABS control unit6. Sensor power supply7. Sensor signal8. Square wave signal generator9. ABS control unit processor