TIAGO

BRAKES

3. Pressure Reduction Phase:

If the ECU detects that the % Slip relative to the

other wheels and vehicle reference speed is still

increasing during the pressure hold phase and the

wheel is tending further towards lock it will start

the pressure reduction phase as the existing

brake pressure in the wheel brake is too high. It

will activate the relevant outlet valve within the

hydraulic modulator, switching it from its normally

closed position to open. This will allow fluid to

pass from the wheel brake into the accumulator

chamber within the modulator. At the same time

the ECU will activate the return pump integrated

into the modulator to draw fluid from the

accumulator and wheel brake and return it to the

TMC. This fluid being returned to the TMC is what

is felt as the pulsations at the pedal, and the

amplitude of the pulsations is relative to the

amount of fluid that needs to be reduced.

Pressure reduction will continue until controlled

wheel returns to the vehicle reference speed.

Solenoid

valve

Electricity

status

Valve

open

Open- close

channel

close

INLET

Master

cylinder

Wheel

cylinder

OUTLET

OPEN

Wheel

cylinder

Reservoir

D.FAIL-SAFE FUNCTION:

If the ABS system detects any fault that may

adversely affect its performance it will switch to a

fail safe shut down mode. When this happens the

electricity supply to the solenoid valves is

deactivated, stopping control signal output, this

causes the valves to switch to their default state.

(Open for inlet valves / Closed for Outlet valves)

The System will light the relevant warning lamp at

the same time to inform the driver the vehicle has

either an ABS or an ABS and EBD failure.

In this condition, the conventional hydraulic brake

circuit will still function, allowing brake pressure to

reach all wheels. It should be noted that with an

ABS fault it will be possible to lock the wheels and

in the Case of an EBD failure the brake force

proportioning between front and rear will no

longer function and hence rear wheel lock is

possible before front.