3308518 - 3340A abs check/adjustment devices

ELECTRO-HYDRAULIC UNIT

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

Electronic control

The electronic control unit is responsible for:

acquiring the data coming from the 'active' wheel rpm sensors
storing control parameters defined during the preparation of the vehicle
storing the control software
processes downloaded data
controls the braking process
detecting failures at the braking system components
memorizing the fault codes and activating the A.B.S. and EBD warning lights.
transmitting and receiving data via the diagnostic connector
conversing with the injection and CAE control units via the CAN line (only for versions with automatic transmission).

Hydraulic control unit

The electro-hydraulic control unit consists of:

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

Responsible for modulating the pressure of the fluid at the brake calipers via two solenoid valves with the following stages:

brake fluid pressure increase
brake fluid pressure maintenance
brake fluid pressure discharge.

The letters indicating to which caliper and to which brake pump outlet they should be connected are stamped on the control unit at each outlet.

RR = to the right rear brake (pipe marked with a light blue coloured band)
LR = to the left rear brake (pipe marked with a green coloured band)
RF = to the right front caliper (pipe marked with a yellow coloured band)
LF = to the left front caliper (pipe marked with a white coloured band)
MC1 = from the T connector (pipe marked with a black or pink coloured band when the pipe polyamide resin is black)
MC2 = from the secondary circuit pump/front.

Pin out

1, Right rear wheel rpm sensor supply 2, Right rear wheel rpm sensor signal 3, Not connected 4, Right front wheel rpm sensor supply 5, Right front wheel rpm sensor signal 6, Left front wheel rpm sensor supply 7, Left front wheel rpm sensor signal 8, Left rear wheel rpm sensor supply 9, Left rear wheel rpm sensor signal 10, Not connected 11, Diagnostic line K 12, Diagnostic line L 13, Not connected 14, Brake pedal switch positive 15, Control unit positive 16, Earth 17, Positive from battery (+ 30) 18, Positive from battery (+ 30) 19, Electronic earth 20, A.B.S. warning light 21, EBD warning light 22, Not connected 23, Not connected 24, Not connected 25, Not connected 26, Not connected 27, Not connected 28, Not connected 29, CAN line (only for versions with automatic transmission) 30, CAN line (only for versions with automatic transmission) 31, Not connected

ACTIVE SENSORS

They consist of two basic elements:

a magnetic multi-polar codifier (1) integrated in the 'instrument' wheel hub bearing
a 'magnetic-resistive' receiver (2) opposite the codifier.

The adoption of active sensors offers the following advantages:

it reduces sensitivity to electro-magnetic interference
it saves weight and size
it simplifies the transmission couplings through the elimination of the phonic wheels.