3308521 - 3350C tcf devices

In addition to the normal functions carried out by the ABS 5.3 (  See subassembly 3340   A(B.S. ANTI-LOCK BRAKING SYSTEM .) ), the versions equipped with T.C.S. (Traction Control System) also have an antislip function.

The T.C.S. function is only activated when the speed of the vehicle is below 40 kph and if the slipping is caused by:

  • a take-off stage
  • fierce acceleration
  • poor adhesion (snow, earth etc. on the road surface)
it intervenes automatically (without the driver operating the brake pedal in any way) on the braking system for the drive wheels.If both drive wheels are slipping, the action of the braking system at the drive wheels is modulated.The control unit excludes the T.C.S. function at brake temperatures above 400 ° C and reactivates it when the temperature goes below 250° C.The exceeding of this temperature threshold is memorized in the control unit.This temperature value is obtained by processing the different parameters linked to the stresses of the brake calipers, the deceleration of the vehicle, etc.Any failures which involve the exclusion of the A.S.R. system are only signalled by the warning light in the instrument panel coming on.

Button/warning light

A warning light in the instrument panel signas:

  • the disengagement of the T.C.S. - warning light on
  • the intervention of the T.C.S. - warning light flashing.
A button allows the T.C.S. antislip function to be excluded; this is signalled by the LED in the button lighting up.
Each time the vehicle is started up the T.C.S. function is activated.

OPERATION

The electro-hydraulic unit on versions equipped with T.C.S. have four extra solenoid valves (8) and (9) which manage the braking in the case of slipping.

Intervention during braking

With the brake pedal depressed, the electronic control unit:

  • does not supply the solenoid valve (N.C.) (8)
  • does not supply the solenoid valve (N.A.) (9).

In this way, the system operates during the following stages:

  • pressure increase
  • pressure maintenance
  • pressure reduction
like the Bosch 5.3 A.B.S. system (  See subassembly 3340   A(B.S. ANTI-LOCK BRAKING SYSTEM .) ).
1, Master cylinder 2, High pressure accumulator 3, Pump 4, Low pressure accumulator 5, Pressurizing solenoid valve 6, Discharge solenoid valve 7, Brake calipers 8, Inlet solenoid valve 9, Operating solenoid valve

T.c.s. intervention

With the drive wheels slipping, the electronic control unit:

  • supplies the hydraulic pump (1)
  • supplies the (N.C.) solenoid valve (2)
  • supplies the (N.A.) solenoid valve (3).
Therefore the pressure produced by the pump (1) arrives at the brake caliper passing through the solenoid valve (6).The operating pressure for the brake caliper is modulated by the solenoid valves (5) and (6).
1, Pump 2, Inlet solenoid valve 3, Operating solenoid valve 4, Brake calipers 5, Pressurizing solenoid valve 6, Discharge solenoid valve

ELECTRO-HYDRAULIC UNIT

It consists of an electronic control unit (1) and an electro-hydraulic control unit (2).
1, Solenoid valves 2, Electronic control unit 3, Electrical connection 4, Relay 5, Electric motor 6, Electro-hydraulic unit casing

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.

Hydraulic control unit

The electro-hydraulic control unit consists of:

  • twelve 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

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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 (+ 15) 16, Power 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, Vehicle speed output (VSO) 23, Not connected 24, T.C.S. LED 25, Not connected 26, Not connected 27, Not connected 28, A.B.S./T.C.S. failure warning light 29, Not connected 30, Not connected 31, T.C.S. button

ACTIVE SENSORS

See description in 3340A - A.B.S. system control/regulation devices