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1) Idling and Normal Braking Condition
In this position, the separation valve and the inlet valve are open (normal open), the electrically operated
shuttle valve and the outlet valve are closed.
When the brake is applied under these conditions, the brake fluid will be sent to each wheel via the
separation valve and inlet valve.
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2) DUMP (ESP is working) Mode
The pressure decreases just before the wheel speed drops and the wheels are locked.
The inlet valve closes and the outlet valve opens as in the ABS HECU and the oil is gathered at the low
pressure chamber while no additional oil is being supplied. Then the pump operates to allow fast oil
drainage. The shuttle valve and the separation valve do not operate while decompression.
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3) HOLD (ESP is working) Mode
The Inlet valve and outlet valve will be closed to maintain the pressure in the hydraulic circuit applied at
the wheels. By closing the valves, the hydraulic pressure at the wheels will not be lost or supplied any
more. During ESP operation, the separation valve closes and only the shuttle valve at the pump opens.
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4) RISE (ESP is working) Mode
The shuttle valve and inlet valve will be open and the separation valve and outlet valve will be closed.
Then, the pump is operated. When ESP operates while the ABS is operating, the pressure will be
increased continuously until just before the corresponding wheel gets locked.
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5) Hydraulic Circuit of HBA
The above figure shows one front and one rear wheel and the same hydraulic circuit forms as in the ESP
operation. When HECU recognizes that it is an emergency and it is required for hard braking, depending
on the pressure value of the brake pressure sensor and pressure changes caused by the pressure sensor
timing, it operates the pump immediately to apply the brake pressure at the wheels. Then, the pressure in
the pump increases until just before the corresponding wheel gets locked. The motor still keeps rotating
and the outlet valve and the separation valve will stay closed. When the wheel starts to lock, the HBA
function cancels and switches to ABS operation.
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7. CIRCUIT DIAGRAM
Wheel speed sensor, Stop lamp switch, Self diagnostic connector, Warning lamp (ABS/ESP)
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1. SPECIFICATION (HPS)
Component Item Specification
Steering wheel Type 3-spoke
Outside diameter
Number of revolutions 3.09 rotations
Heated wire Simple ON/OFF
Gear box Type Rack and pinion
Gear ratio 46.94
Rack stroke
Steering angle Inner
Outer
Wheel alignment Toe-in
Oil pump Type Vane (removable pump and reservoir)
Maximum pressure
Displacement
Pulley diameter
Steering column Tilting angle Up + 2.0 deg
Down - 3.0 deg
Lower shaft Type Ball slip
Steering oil Oil type S-PSF 3
Oil reservoir capacity
Change interval EU (Diesel): Check and add at every 20,000
km
GEN (Diesel, Gasoline): Check and add at
every 15,000 km
Turning capability Min. turning radius 5.35 m
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2. TIGHTENING TORQUE
Item Tightening torque Remark
1. Power steering reservoir mounting bolt 8.8 to 13.7 Nm 12 mm x 2 EA
2. Power steering
pumpUpper mounting bolt/nut
13 mm x 1 EA
Lower mounting bolt
12 mm x 2 EA
3. Oil pipe Eye bolt (pump side) 53.9 to 63.7 Nm 22 mm
Steering gear box side nut 31.4 to 37.2 Nm 17 mm
4. Oil pipe bracket mounting nut 6.8 to 10.8 Nm 10 mm
5. Tie rod end lock nut 44.1 to 53.9 Nm 17 mm
6. Tie rod nut 63.7 to 78.4 Nm 22 mm
7. Lower shaft Lower mounting bolt
(gear box side)17.6 to 24.5 Nm 12 mm
Upper mounting bolt (column
side)17.6 to 24.5 Nm 12 mm
8. Column shaft Lower mounting bolt 19.6 to 24.5 Nm 12 mm
Upper mounting nut 19.6 to 24.5 Nm 12 mm
9. Steering wheel nut 39.2 to 49.1 Nm 22 mm
10. Loosened gear box mounting bolt/nut Left: 98.0 to 127.4 Nm 17 mm
Right: 88.3 to 107.9 Nm 17 mm
11. Heat shield mounting bolt 8.8 to 13.7 Nm 12 mm x 2 EA