Sensotronic Brake Control

(SBC)

1
327 HO 09 SBC (WJB) 03-05-04
R230 and W211: Starting MY2003
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 Objectives
At the end of this presentation, you should be able to:
1. Explain the function of and purpose for SBC
2. Describe the customer interface with SBC
3. List the hydraulic and electronic components used for SBC
4. Describe how the “normal” feel of the brake pedal is maintained
5. Explain emergency operation of the SBC braking system
6. Describe “temperature compensation”
7. Explain “Deactivation” and describe when it is necessary to do it
8. “Activate” the SBC system
9. Locate tools and the proper procedure for bleeding brakes

These technical training materials are current as of the date noted on the materials, and may be revised or updated without notice. Always check for revised or updated information.
To help avoid personal injury to you or others, and to avoid damage to the vehicle on which you are working, you must always ref er to the latest Mercedes -Benz Technical Publication and follow all
pertinent instructions when testing, diagnosing or making repair.
Illustrations and descriptions in this training reference are based on preliminary information and may not correspond to the final US version vehicles. Refer to the official introduction manual and WIS
when available. Copyright Mercedes-Benz USA, LLC, 2004
WIS document numbers shown apply to WIS Version USA/CDN at date of writing.
2
Reproduction by any means or by any information storage and retrieval system or translation in whole or part is not permitted without written authorization from Mercedes -Benz USA, LLC or it's
successors. Published by Mercedes -Benz USA, LLC Printed in U. S.A.

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 Contents
Advantages of SBC 5
Driving with SBC 8
SBC components 13
Brake operating unit (BOU) 17
Traction system hydraulic unit 27
Three pressure stages 32
Temperature Compensation 38
Deactivation 39
System activation 42
Bleeding the system 49

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SBC Incorporates these Functions:

ABS (Anti lock Brakes 1984)

+ ASR (Automatic Slip Regulation 1991)
+ ETS (Electronic Traction System 1995)
+ ESP (Electronic Stability Program 1996)
+ BAS (Brake Assist System 1998)

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 Advantages of SBC
• Improves metering of required brake pressure
– each wheel can be precisely controlled
• Improved BAS function
– monitors release of accelerator pedal and application of
brake
– maximum pressure available immediately
– pre-filling of system (overcoming play)
– when the BAS function is anticipated, slight pressure is
applied

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 Advantages of SBC

• Electronic Brake Proportioning: EBP

– allows brake proportioning front to back and side to side
• No pedal vibration during ABS operation
– eliminates “distraction” to the driver during critical moments
– indicator light in instrument cluster signals traction loss
• Improved driving dynamics: ABS, ASR, and ESP
– faster response to brake request inputs

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 Advantages of SBC

• Pressure reduction at standstill

– reduces stress on components
• Dry braking function
– wiper input via CAN
– ~every 7 to 14 minutes
– brake actuation changes
time interval

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 Driving with SBC - Wake-Up

SBC is functional as soon as it is “wakened” by:

• opening a door (via CAN)

• operating the central locking system (via CAN)

• depressing the brake pedal

• turning key to position 1

• operating parking brake

•The Wake-Up may be followed by a Pre-Drive self

Check performed by SBC 8

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Driving with SBC – Pre-Drive Check (PDC)

When SBC performs a PDC after a "wake-up", the following are

checked:
Warning! Pressure is applied to brake calipers (~60 bar)
• reservoir pressure (if low, it will be corrected by running the
high pressure charge pump in the hydraulic unit)
• pressure sensors
• control valves
• leak tests
• operational checks
Note: self-tests are constantly conducted during driving (~ once every 16
brake applications) 9

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Driving with SBC – Delayed Off Function

Time that SBC remains operational after use:

• with vehicle stationary and was locked = 20 seconds

• with vehicle stationary and ignition in “0”,

brake pedal not operated = 2 minutes

• with vehicle stationary, ignition in “0”,

brake pedal operated in delayed off phase and
released again = 4 minutes

10

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 Warning Display

Complete ESP control module failure -

Instrument cluster will scroll through failure displays
11

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 Warning Display
SBC control module failure

Certain faults will trigger audible signal 12

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SBC Components

• Brake Operating Unit (BOU)

• Wheel speed sensors

• Traction System Hydraulic

Unit (A7/3)
13

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 W211 System Overview

Circuit 30 Brake lights

Rear SAM
(N10/2)
Circuit 87
SBC
Circuit 31 SBC CAN ESP control
control Wheel module (N47/5)
Wheel speed sensors module speeds

L6/1, L6/2, L6/3, L6/4 (A7/3n1)

Wake up
Brake lights Front
Stop lamp switch Speed status SAM
(S9/1) Diagnostics (N10/1)

SBC pedal travel

Diagnostic connector
sensor (B37/1)
(X11/4)

14

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 R230 System Overview

Circuit 30 Brake lights

Rear SAM
(N10/8)
Circuit 87
Diagnostic connector
Circuit 31 SBC (X11/4)
control
Wheel speed sensors module SBC
L6/1, L6/2, L6/3, L6/4 (A7/3n1) CAN ESP control
Stop lamp switch Wheel module (N47/5)
speeds

(S9/1)
Wake up
SBC pedal travel Brake lights
Passenger side
sensor (B37/1) Speed status
SAM (N10/11)

15

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 X11/4 Diagnosis Connection

R230 W211
A7/3n1 A7/3n1
SBC SBC

N47/5 X11/4
ESP N10/1
L.F.SAM
X11/4 Z70/4
N15/5 Pin 9
ESM
Z6/33
Pin 9
N47/5
N51/2
ESP
ABC

16

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Brake Operating Unit - (BOU)

17

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Brake Operating Unit
The Brake Operating Unit (BOU)
consists of the following:

• Brake fluid reservoir

(Do not overfill!)

• SBC pedal value sensor

• Tandem master cylinder

• Brake pressure simulator

(Note: no vacuum booster)

18

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Master Cylinder

• Fluid level sensor

• Fluid return line

• Do not overfill

• Hydraulic lines to SBC

• Supply hose to SBC

19

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Fluid Reservoir Cover

• Ultraviolet protection
(211 only)

20

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Pedal Value Sensor - (B37/1)
• Contains two hall effect sensors

• Converts pedal travel value to

an electrical signal
• Provides input to SBC
control module A7/3

21

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 BOU Tandem Master Cylinder

Fluid reservoir
Fill valves

Primary piston

Floating piston

A7/3 - Traction system hydraulic

unit with separation valves y1 and
y1 y2 y2

A7/3
Brake pressure simulator
22
GF42.46-P-4200-03SL

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 Normal Braking - Light Pressure

• Driver applies
pressure to the
brake pedal

• Fill valves close

• Pedal travel sensor

sends a signal to A7/3

• y1 and y2 energized,
preventing fluid
movement externally

• Floating piston allows

fluid to enter simulator,
compressing the light
y1 y2 spring, providing pedal
feel to the driver
A7/3 23
GF42.46-P-4200-03SL

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 Normal Braking - Increased Pressure

• Increasing pedal
travel causes the
larger spring to
y1 y2 compress, providing
harder pedal feel
A7/3 24

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 Normal Braking - Strongest Feedback

• Further pedal travel

causes piston to
compress rubber
bumper, providing
greatly increased
y1 y2 pedal pressure

A7/3 25

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 Emergency Operation

• All electrical functions

canceled

• Hydraulic pressure
created with NO
power assist

• Pressure directed
through A7/3 y1 and
y2 to ....

Left Front and

Right Front calipers
only!

y1 y2
Left front Right front
A7/3 26
GF42.46-P-4200-03SL
GF42.46-P-3000SL

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Traction System Hydraulic Unit (A7/3)

Consists of:

• SBC control module (A7/3n1)

• High pressure charge pump

(A7/3m1)

• Pressure reservoir

27

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Traction System Hydraulic Unit
A7/3

28
GF42.50-P-4000-03S

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 Legend

1 Brake Operating Unit A7/3y1 Left front separation valve

2 Brake pressure simulator A7/3y2 Right front separation valve
3 Pressure reservoir A7/3y3 Front axle balance valve
7 Left front media separator A7/3y4 Rear axle balance valve
(dividing piston) A7/3y6 Left front intake control valve
8 Right front media separators A7/3y7 Left front outlet control valve
(dividing piston) A7/3y8 Right front intake control valve
A7/3 Traction system hydraulic unit A7/3y9 Right front outlet control valve
A7/3b1 Front axle pre-pressure sensor A7/3y10 Left rear intake control valve
A7/3b2 Reservoir pressure sensor A7/3y11 Left rear outlet control valve
A7/3b3 Left front pressure sensor A7/3y12 Right rear intake control valve
A7/3b4 Right front pressure sensor A7/3y13 Right rear outlet control valve
A7/3b5 Left rear pressure sensor B37/1 SBC pedal value sensor
A7/3b6 Right rear pressure sensor S9/1 Stop lamp switch (4-pin)
A7/3m1 High-pressure charge pump

29

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Emergency Operation Circuit

• Pressure applied directly

to front calipers
• y1 and y2 not energized
• b1, b3, and b4 pressure
sensors may provide
information to SBC control
module
• Media separator/Dividing
piston 7 and 8 isolate
emergency circuit from
normal circuit

30
GF42.46-P3000SL

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 Brake Pressure Supply

• pressure reservoir charged to

160 bar
• the high pressure charge pump
runs as needed
• pressure blocked by y6, y8,
y10, y12 31
GF 42.50-P-4000-04S
GF42.46-P-0001SL

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 Three Pressure Stages

Same pressure stages as used with ABS functions:

• Pressure apply

• Pressure hold

• Pressure release

32

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 Pressure Apply - Rear Wheels

Brake pedal pressure

Reservoir pressure

• Brake pedal depressed

• B37/1 and b1 report brake
application to control module
• y1 and y2 energized
• y10 and y12 intake control valves
energized
• Pressure at each rear wheel
monitored by b5 and b6
• Balance valve y4 not energized GF42.50-P-4000-04S33
GF42.46-P-1000SL
GF42.46-P-4500-02SL

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Pressure Apply - Front Wheels

Brake pedal pressure

Reservoir pressure

• y6 and y8 energized
• pressure applied to left and
right dividing pistons 7 and 8
• 7 and 8 apply pressure to caliper
• pressure at each wheel monitored
by b3 and b4
• Balance valve y3 not energized
34
GF42.50-P-4000-04S
GF42.46-P-1000SL

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 Pressure Apply - All Wheels

• Outlet control valves y7, y9, y11, y13 energized 35

GF42.50-P-4000-04S
GF42.46-P-1000SL

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Pressure Hold - All Wheels

• y6, y8, y10, y12 de-energized

36
GF42.50-P-4000-04S
GF42.46-P-1000SL

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Pressure Reduction - All Wheels

• y7, y9, y11, y13 de-energized

37
GF42.50-P-4000-04S
GF42.46-P-1000SL

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Temperature Compensation

During continuous brake use the

fluid in the calipers expand, this:
• creates high pressure
• prevents valves 7 & 8 from moving

To reduce this pressure, y1 and

y2 are pulsed
38

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 Deactivation

SBC must be deactivated with SDS before any work is performed

on the system. This will prevent the pre-drive check from being
automatically performed which could cause injury.

Deactivating the system will:

• empty the pressure reservoir

(a lower pressure with no volume may be retained)

• prevent the charge pump from operating

•Note: the warning buzzer is deactivated when accessing

SBC with the SDS.

39

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 Deactivation

SBC must be deactivated PRIOR to:

• working on the hydraulic system

• removing or installing brake pads

• replacing rotors

• replacing the pressure reservoir

• replacing the BOU

• replacing the SBC hydraulic unit (A7/3)

40

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 Deactivation

Charge pump disabled and accumulator fluid returned to the reservoir!

41
Pressure at A7/3b2

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 System Activation

Activation must be performed anytime the system has been

deactivated, BEFORE the engine is started!

Failure to activate will prevent proper operation and create fault

codes!

Activating SBC with SDS will:

• charge the accumulator
• perform a Predrive Check
• move the pads towards the rotors with ~60 bar pressure
• erase the fault memory

(Note: may have to activate several times to position the brake pads)

42

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System Activation

43

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Activation - Left Front

Caliper held with ~60 bar 44

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Activation - Right Front

Caliper held with ~60 bar 45

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Activation - Right Rear

Caliper held with ~60 bar 46

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Activation - Left Rear

Caliper held with ~60 bar 47

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Activation - Recharge

48

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 Bleeding the Brake System

Proper system bleeding is critical!

Follow directions in SDS

• Bleeding must be performed using the SDS

• Pressure at bleeder valves will exceed 100 bar

(Hold the bleeder hose securely)

• Bleeding may require ~1.5 hours

• Bleeding may use ~ 1.5 liters of brake fluid

49
AR42.10-P-0012R

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Equipment Required

• Pressure bleeder
• Adapters
• Fluid receptacle
• SDS - follow instructions carefully

211 589 01 91 00

CAUTION:
Extremely high pressure at bleeder!
AR42.10-P-0010-02R 50
AR42.10-P-0012R
WS42.00-P-0048B

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 Bleeding the Brake System
Connect equipment and follow steps in SDS

51
AR42.10-P-0012R

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 Acronym List
(Used in This Handout.)

ABS - Anti-lock Brake System

ASR - Anti Slip Regulation
BAS - Brake Assist System
BOU - Brake Operating Unit
CAN - Controller Area Network
EBP - Electronic Brake Proportioning
EBR - Electronic Brake Regulation
E-Gas - Electronic Accelerator
ESP - Electronic Stability Program
ETS - Electronic Traction System
PDC - Predrive Check
SAM - Signal Acquisition Module
SBC - Sensotronic Brake Control 52

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 Appendix

AR42.10-P-0010I Carrying out bleeding operation

AR42.10-P-0012R Bleeding system with Star Diagnosis
GF42.45-P-0001-04SL ESP driver information
GF42.45-P-0001SL ESP function
GF42.45-P-2000SL ESP brake moment control
GF42.45-P-3500SL ASR control mode function
GF42.46-P-0001SL SBC function
GF42.46-P-1000SL SBC Normal braking function
GF42.46-P-2000SL SBC additional braking functions
GF42.46-P-3000SL SBC braking with malfunction
GF42.46-P-4200-03SL BOU function
GF42.46-P-4210SL SBC pedal value sensor
GF42.46-P-4500-02SL SBC control module – task
GF42.50-P-4000-03S Hydraulic unit design
GF42.50-P-4000-04S Hydraulic unit function
GF42.50-P-4000S Hydraulic unit task/location/function
WS42.00-P-0048B EHB adaptor

53

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