lowing diagrams show only the right front wheel in
an antilock braking operation.
NORMAL BRAKING HYDRAULIC CIRCUIT AND
SOLENOID VALVE FUNCTION
The hydraulic diagram (Fig. 6) shows the vehicle in
the normal braking mode of the base brake hydraulic
system. The diagram shows no wheel spin or slip
occurring relative to the speed of the vehicle. The
driver is applying the brake pedal which builds pres-
sure in the brake hydraulic system to engage the
brakes and stop the vehicle.
ABS HYDRAULIC CIRCUIT AND SOLENOID VALVE
FUNCTION (ABS WITHOUT TRACTION CONTROL)
The hydraulic diagram (Fig. 7) shows the vehicle in
the ABS braking mode. The diagram shows one
wheel is slipping because the driver is attempting to
stop the vehicle at a faster rate than is allowed by
the surface on which the tires are riding.
• The normally open and normally closed valves
modulate (build/decay) the brake hydraulic pressure
as required.
• The pump/motor is switched on so that the
brake fluid from the low pressure accumulators is
returned to the master cylinder circuits.
• The brake fluid is routed to either the master
cylinder or the wheel brake depending on the posi-
tion of the normally open valve.
NORMAL BRAKING HYDRAULIC CIRCUIT,
SOLENOID VALVE, AND SHUTTLE VALVE
FUNCTION (ABS WITH TRACTION CONTROL)
The hydraulic diagram (Fig. 8) shows a vehicle
with traction control in the normal braking mode.
The diagram shows no wheel spin or slip occurring
relative to the speed of the vehicle. The driver is
applying the brake pedal which builds pressure in
the brake hydraulic system to engage the brakes and
stop the vehicle. The hydraulic shuttle valve closes
Fig. 6 Normal Braking Hydraulic Circuit
1 – OUTLET VALVE
2 – PUMP PISTON
3 – PUMP MOTOR (OFF)
4 – LOW PRESSURE ACCUMULATOR
5 – NORMALLY CLOSED VALVE (OFF)
6 – TO RIGHT FRONT WHEEL
7 – NORMALLY OPEN VALVE (OFF)
8 – MASTER CYLINDER PRESSURE
9 – FROM MASTER CYLINDER
10 – NOISE DAMPER CHAMBER
LH BRAKES 5 - 61
DESCRIPTION AND OPERATION (Continued)
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