The pushing force pulls the caliper inward which pulls the outer brake pad into the rotor. When
the EPB is released, the ball nut is reversed and the square cut caliper seal pulls the piston away
from the inner brake pad and releases tension to the caliper and the outer brake pad.

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Note:

New Technology Training

(Module 926)

The caliper and motor are not serviceable. Do not disassemble for inspection or
diagnosis. Calipers and motors are available as replacement parts and can be
ordered separately or as an assembly.

A dust seal O-ring is positioned around the circumference of the caliper to seal the motor to the
caliper. This O-ring should be replaced if the motor is ever removed from the caliper.
The motor output gear is splined to the ball nut worm gear.

8-13

8-14

Dust O-ring and Ball Nut Worm Gear

EPB Motor Drive

The ball nut moves up and down on the threads of the worm gear to apply and release mechanical
pressure to the back or inside face of the hydraulic piston.

8-15

8-16

Worm Gear

Note:

Ball Nut and Piston

The physical fit of the ball nut to the piston provides areas that can trap air. Air
bleeding procedures are the same as existing models. Brake pedal stroke length
should always be checked after installing a new caliper or brake component to
ensure all air is removed from the brake system.

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New Technology Training

(Module 926)

The ball nut is constructed of many ball bearings and keeper springs that provide for smooth
movement and strength. A flat edge made onto each side of the ball nut keys into the notches
made into the inside of the hydraulic piston.

8-17

8-18

Ball Nut Bearings

Piston Internal View

As the piston moves towards the inner brake pad, the serrations machined into the outer face of
the piston bite into the inner brake pad shim (permanently mounted to the brake pad) to prevent
the piston from rotating when mechanical force begins to increase. Do not lubricate or apply
any anti-seize paste to this area.

8-20

8-19
Piston Serrations

Caliper Hydraulic Seals

The notches located at 12:00 and 6:00 in this picture are used to turn the piston clockwise when
the Subaru Select Monitor is not available.
Note:

The service notches can be located in any direction and have no affect to
hydraulic or parking brake operation.

The piston must be turned during service work to rotate the ball nut back to a service park position
if the Subaru Select Monitor is not available.

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New Technology Training
EPB Electrical Operation and Control

(Module 926)

The operation of the EPB at each rear brake caliper is accomplished using two wires that operate
the bidirectional movement of the EPB motors. There are no sensors incorporated into the caliper.
Sensing for apply and release is determined by the amount of amperage measured in the Hydraulic
Control Unit.
MB-8
SBF-15
(B)

*3

W/G

W/R

C15

P

W/G

i87

i163

*2

EPB CONTROL SWITCH

EPB ON

LOCK

HILL HOLD
SWITCH

W/G

C:

C15

FB-52
F/B FUSE NO. 10
(IG)

*1

C: i192

GR

AUDIO

MB-7
M/B FUSE NO. 33
(B)

Y

FB-45
F/B FUSE NO. 3
(IG)

R/Y

FB-71
F/B FUSE NO. 14
(B)

RELEASE

7

GR

12

W/G

2

B

1

Y

6

P

5

P

1

G

4
i156
REAR BRAKE
CALIPER LH

R

2

W

1

REAR BRAKE
CALIPER RH

LG

BRAKE FLUID
LEVEL SWITCH

2

1

2

1

R149
G

R

2

W

1

R153

R140

W

R

Y

R36
L

R35
24

W/G
23

Y

B
25

i112

26

B16

28

LG

2

P

BR/Y

27

1

R154

6

5

3

2

B60

R40

Y/G
4

3

Y/B

Y/L
2

1

Y

i128

i112

B

BR/Y

LG/R

P/G

Y/W

B/G

W/V

G

W/R

R/Y

Y

Y

Y/L

Y/B

Y/G

46

8

21

26

20

19

3

6

33

16

5

45

44

34

35

B

5

B

B60

J/C
B479

REF. TO GND [k]

B310

VDC CM

GV

8-21
EPB Wiring Schematic

During apply control, the polarity of the wires is controlled to turn the ball nut counter clockwise.
This will screw the ball nut into the piston and place mechanical force on the inner brake pad
and pull the caliper inward to force the outer brake pad into the rotor. An initial current spike will
occur as the motor first starts to turn and then level off as the motor turns without opposing any
mechanical force. As the Hydraulic piston makes contact with the inner brake pad, current starts
to increase and continues to increase as the brake caliper is pulled inward. The amperage will
reach maximum level after both brake pads are contacting the rotor with a predetermined amount
of mechanical force.

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New Technology Training

(Module 926)

8-22
EPB ON

Time is measured during the application of the EPB until a pre-established amperage level is
reached. This represents the normal EPB on state. This value is also used to determine how long
to operate the motor in the reverse direction when the EPB is turned off. As the brake pads wear,
the ball nut parks at a lower position on the worm gear. The EPB release motor operation time,
determines the final position.

8-23
EPB OFF

Note:

The amount of time and amperage needed to release the EPB is always lower
than the application time and amperage due to the reduced work load.

During EPB release, the polarity of the wires to the EPB motor is reversed and the ball nut rotates
clockwise to release the mechanical tension on the inner brake pad and caliper.

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Content
Power supply
Power supply
Front LH wheel

Signal
Power supply

Front RH wheel
ABS wheel speed sensor

Signal
Power supply

Rear LH wheel

Signal

(Module 926)

Terminal
No.
(+) — (–)

Input/Output signal
Measured value and measuring conditions

5 — 46

10 — 15 V when the ignition switch is ON.

41 — 46

0 — 18 V

40

7 — 14 mA: Rectangle waveform

37 — 46

0 — 18 V

36

7 — 14 mA: Rectangle waveform

39 — 46

0 — 18 V

38

7 — 14 mA: Rectangle waveform

43 — 46

0 — 18 V

42

7 — 14 mA: Rectangle waveform

Valve relay power supply

16 — 46

10 — 15 V when the ignition switch is ON.

Motor relay power supply

33 — 46

10 — 15 V when the ignition switch is ON.

Stop light switch

17 — 46

1.5 V or less when the stop light is OFF; otherwise, 10 —
15 V when the stop light is ON.

Brake light relay power supply

27 — 46

10 — 15 V when the ignition switch is ON.

Rear RH wheel

Power supply

New Technology Training

Signal

Vehicle speed output signal

24

VDC OFF switch

0

12 V pulse

1 — 46

1 Ω or less when the OFF switch is “ON”; 1
MΩ or more when the switch is “OFF”.

Parking brake switch

19

Pulse signal

Parking brake switch

20

Pulse signal

Parking brake switch

21