brake MERCEDES-BENZ SPRINTER 2006 User Guide

TEST ACTION APPLICABILITY
4 Turn the ignition off.
Disconnect the DRBIIItfrom the DLC.
Disconnect the Shifter Assembly harness connector.
Turn the ignition on.
Using a 12-volt test light connected to ground, probe the K-ABS, Shifter Assembly
circuit.
NOTE: The test light must illuminate brightly. Compare the brightness to
that of a direct connection to the battery.
Does the test light illuminate brightly?All
Ye s!Go To 5
No!Go To 6
5 Turn the ignition off.
Disconnect the Controller Antilock Brake harness connector.
Turn the ignition on.
Using a 12-volt test light connected to ground, probe the K-ABS, Shifter Assembly
circuit.
NOTE: The test light must illuminate brightly. Compare the brightness to
that of a direct connection to the battery.
Does the test light illuminate brightly?All
Ye s!Repair the K-ABS, Shifter Assembly circuit for a short to voltage.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No!Replace the Controller Antilock Brake in accordance with the
service information.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
6 Turn the ignition off.
Disconnect the Shifter Assembly harness connector.
Disconnect the DRBIIItfrom the DLC.
Measure the resistance of the K-ABS, Shifter Assembly circuit between the Shifter
Assembly connector and the DLC.
Is the resistance below 5.0 ohms?All
Ye s!Replace the Shifter Assembly in accordance with the Service
Information.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No!Repair the K-ABS, Shifter Assembly circuit for an open.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
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COMMUNICATION
*NO RESPONSE FROM SHIFTER ASSEMBLY ÐContinued

Symptom:
NO CAN COMMUNICATION WITH ABS
POSSIBLE CAUSES
DTC PRESENT
OPEN CAN CIRCUITS AT INSTRUMENT CLUSTER
INSTRUMENT CLUSTER
CHECK POWERS AND GROUNDS TO THE AFFECTED MODULE
OPEN CAN CIRCUITS AT CAB
CONTROLLER ANTILOCK BRAKE
TEST ACTION APPLICABILITY
1 With the DRBIIIt, record and erase DTC's.
Cycle the ignition switch from ON to OFF to ON.
With the DRBIIIt, read DTC's.
Did this DTC reset?All
Ye s!Go To 2
No!The conditions that caused this code to set are not present at this
time. Using the wiring diagram/schematic as a guide, inspect the
wiring and connectors for an intermittent condition.
Perform BODY VERIFICATION TEST - VER 1.
2 With the DRBIIIt, check the TCM, ECM, and the Shifter Assembly for this same or
similar ABS message error DTC.
Is the same or similar DTC set in the other modules?All
Ye s!Go To 3
No!Go To 5
3 Turn the ignition off.
Disconnect the Controller Antilock Brake harness connector.
Check each power and ground circuit to the module.
Were any problems found?All
Ye s!Refer to the wiring diagrams located in the service information to
help isolate an open or shorted condition. Repair as necessary.
Perform BODY VERIFICATION TEST - VER 1.
No!Go To 4
4 Turn the ignition off to the lock position.
Disconnect the Controller Antilock Brake harness connector.
Measure the resistance between the CAN C Bus (+) circuit and the CAN C Bus (-)
circuit in the CAB harness connector.
Is the resistance 60 ohms,   3.0 ohms?All
Ye s!Replace the Controller Antilock Brake in accordance with the
service information.
Perform BODY VERIFICATION TEST - VER 1.
No!Repair the CAN C Bus (+) or the CAN C Bus (-) circuit for an open.
Perform BODY VERIFICATION TEST - VER 1.
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INSTRUMENT CLUSTER

CLOCKSPRING C2 - YELLOWCAV CIRCUIT FUNCTION
1 20VT DRIVER AIRBAG SQUIB 1 LINE 1
2 20DG DRIVER AIRBAG SQUIB 1 LINE 2
CONTROLLER ANTILOCK BRAKECAV CIRCUIT FUNCTION
1 12BR GROUND
2 12RD FUSED B(+)
3- -
4- -
5 14BR GROUND
6 14RD FUSED B(+)
7- -
8 20BK/DG SENSOR SIGNAL
9 20YL/WT SENSOR SIGNAL
10 20YL/RD SENSOR SIGNAL
11 18BL/BK K-ABS/SHIFTER ASSEMBLY
12 18BK LEFT FRONT WHEEL SPEED SENSOR (+)
13 - -
14 20WT LEFT REAR WHEEL SPEED SENSOR (+)
15 18BR RIGHT FRONT WHEEL SPEED SENSOR (-)
16 18BK RIGHT FRONT WHEEL SPEED SENSOR (+)
17 - -
18 - -
19 - -
20 20WT BRAKE SWITCH OUTPUT
21 20BR GROUND
22 - -
23 18BK/RD FUSED OPTIONAL EQUIPMENT RELAY OUTPUT
24 20DG/WT CAN C BUS (+)
25 20BR SENSOR GROUND
26 20WT/GY BRAKE PRESSURE SENSOR SIGNAL
27 18BK/BL TCS SWITCH (ASR) SENSE
28 18BR LEFT FRONT WHEEL SPEED SENSOR (-)
29 20BR LEFT REAR WHEEL SPEED SENSOR (-)
30 20BR RIGHT REAR WHEEL SPEED SENSOR (-)
31 20YL RIGHT REAR WHEEL SPEED SENSOR (+)
32 18BK/RD BRAKE LAMP SWITCH OUTPUT
33 - -
34 - -
35 - -
36 - -
37 - -
38 - -
39 20RD/BL POWER INPUT
40 20DG CAN C BUS (-)
41 20DG/YL SENSOR SIGNAL
42 20WT/RD 5 VOLT SUPPLY
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CONNECTOR PINOUTS

INSTRUMENT CLUSTER C1CAV CIRCUIT FUNCTION
1 20BR FUEL LEVEL SENSOR SIGNAL RETURN
2 20BR/DG AMBIENT TEMPERATURE SENSOR SIGNAL RETURN
4 20WT/GY K-IC/ATC/HBM/CHM
5 20BR/BK PARK BRAKE INDICATOR SIGNAL
7 20BK/DG RIGHT TURN SIGNAL
10 20BL/BK FUEL LEVEL SENSOR SIGNAL (+)
11 20BL/DG AMBIENT TEMPERATURE SENSOR SIGNAL (+)
14 20DG/WT/BL ENGINE COOLANT LEVEL SWITCH SIGNAL
15 20BR/WT FRONT COURTESY LAMPS CONTROL
16 20YL/RD SEAT BELT SWITCH SIGNAL
17 20DG CAN C BUS (-)
18 20DG/WT CAN C BUS (+)
INSTRUMENT CLUSTER C2 - WHITECAV CIRCUIT FUNCTION
1- -
2- -
3 20RD/YL FUSED B(+)
4 20BR/WT BRAKE WEAR SENSOR SIGNAL
5- -
6 18BR GROUND
7 20GY/DG/RD LAMP DRIVER
8 20BL/WT FUSED HIGH BEAM SWITCH OUTPUT
9 20BL/RD/WT VEHICLE SPEED SENSOR OUTPUT
10 20BK FUSED IGNITION SWITCH OUTPUT (RUN-START)
11 20BL/BK KEY-IN IGNITION SWITCH SIGNAL
12 - -
13 20BK/WT LEFT TURN SIGNAL
14 20BR/YL BRAKE FLUID LEVEL INDICATOR SIGNAL
15 20BL GENERATOR FIELD DRIVER
16 20YL AIRBAG WARNING INDICATOR DRIVER
17 - -
18 20BL/VT D(+) RELAY NO. 1 CONTROL
18 20BL/VT D(+) RELAY NO. 1 CONTROL
INTRUSION SENSOR NO. 1 - BLACKCAV CIRCUIT FUNCTION
1 20BR GROUND
2 20DG/BK INTRUSION SENSOR 1 SIGNAL
3 20DG/YL INTRUSION SENSOR INTERFACE
4 20RD/DG FUSED B(+)
INTRUSION SENSOR NO. 2 - BLACKCAV CIRCUIT FUNCTION
1 20BR GROUND
2 20GY/BK INTRUSION SENSOR 2 SIGNAL
3 20DG/YL INTRUSION SENSOR INTERFACE
4 20RD/DG FUSED B(+)
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CONNECTOR PINOUTS

SECURITY SYSTEM MODULE C2 - LT. GREENCAV CIRCUIT FUNCTION
1 16DG/YL INTRUSION SENSOR INTERFACE
2 16GY/BL WINDOW DEFOGGER-LEFT REAR OUTPUT
3 16GY WINDOW DEFOGGER RELAY-RIGHT REAR OUTPUT
4 20DG/BK INTRUSION SENSOR 1 SIGNAL
5- -
6- -
7 20GY/BK INTRUSION SENSOR 2 SIGNAL
8 16GY/DG K-CTM/SSM
9 18BK/BL SIREN SIGNAL CONTROL
10 20DG/WT/BL INTRUSION SENSOR 3 SIGNAL
11 16WT/BL RKE INTERFACE
12 16WT/BL/RD SECURITY SYSTEM INTERFACE
SENTRY KEY REMOTE ENTRY MODULE (SKREEM)CAV CIRCUIT FUNCTION
1 18YL RKE ANTENNA
2 16BR GROUND
3 16RD/YL FUSED B(+)
4 16BK/WT LEFT TURN SIGNAL
5 20DG/WT CAN C BUS (+)
6 20DG CAN C BUS (-)
7 16BK/YL FUSED IGNITION SWITCH OUTPUT (RUN-START)
8 20WT/DG K-SKREEM
9 16WT/BL/RD (EXCEPT
VTSS)RKE INTERFACE
9 16WT/BL/RD (VTSS) SECURITY SYSTEM INTERFACE
10 18DG/YL TURN SIGNAL/ANTI-THEFT ALARM RELAY-LEFT/RIGHT CONTROL
11 20BR TRANSPONDER COIL (+)
12 - TRANSPONDER COIL (-)
SHIFTER ASSEMBLY - BLACKCAV CIRCUIT FUNCTION
1- -
2 20GY/DG/RD LAMP DRIVER
3 20BL/DG K-ABS/SHIFTER ASSEMBLY
4 18BR GROUND
5 20BK/BL/RD BRAKE LAMP SWITCH
6 20DG/WT CAN C BUS (+)
7 20DG CAN C BUS (-)
8 18BK/DG TRANSMISSION RELAY OUTPUT
9 16WT/BL/RD FUSED IGNITION SWITCH OUTPUT (RUN-START)
10 16WT/RD BACK-UP LAMP
SIREN - BLACKCAV CIRCUIT FUNCTION
1 18RD/DG FUSED B(+)
2 18BR GROUND
3 18BK/BL SIREN SIGNAL CONTROL
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CONNECTOR PINOUTS

TABLE OF CONTENTS
1.0 INTRODUCTION.........................................................1
1.1SYSTEM COVERAGE...............................................1
1.2SIX-STEP TROUBLESHOOTING PROCEDURE..........................1
2.0 INDENTIFICATION OF SYSTEM............................................1
3.0 SYSTEM DESCRIPTION AND FUNCTIONAL OPERATION......................1
3.1ESP ..............................................................1
3.2ABS ..............................................................1
3.3BRAKE ASSIST SYSTEM (HBA).......................................2
3.4TCS (ASR).........................................................2
3.5ELECTRONIC BRAKE DISTRIBUTION (EBD)............................2
3.6VEHICLE CONTROLLING (FZR).......................................2
3.7SYSTEM COMPONENTS.............................................2
3.7.1ABS AND TCS (ASR) INDICATORS............................3
3.7.2CONTROLLER ANTILOCK BRAKE (CAB).......................3
3.7.3HYDRAULIC CONTROL UNIT (HCU)...........................3
3.7.4SWITCHES/SENSORS.......................................3
3.7.5SELF TESTS...............................................4
3.8USING THE DRBIIIT.................................................4
3.9DRBIIITERROR MESSAGES.........................................4
3.9.1DRBIIITDOES NOT POWER UP (BLANK SCREEN)...............5
3.9.2DISPLAY IS NOT VISIBLE....................................5
4.0 DISCLAIMERS, SAFETY, WARNINGS.......................................5
4.1DISCLAIMERS......................................................5
4.2SAFETY...........................................................5
4.2.1TECHNICIAN SAFETY INFORMATION..........................5
4.2.2VEHICLE PREPARATION FOR TESTING........................5
4.2.3SERVICING SUB-ASSEMBLIES...............................5
4.2.4DRBIIITSAFETY INFORMATION...............................6
4.3WARNING.........................................................6
4.3.1VEHICLE DAMAGE WARNINGS...............................6
4.3.2ROAD TESTING A COMPLAINT VEHICLE.......................6
4.4DIAGNOSIS........................................................6
5.0 REQUIRED TOOLS AND EQUIPMENT......................................7
6.0 GLOSSARY OF TERMS...................................................7
7.0 DIAGNOSTIC INFORMATION AND PROCEDURES............................9
BRAKES (CAB)
ANTI-LOCK BRAKE MODULE INTERNAL...................................10
CAB INTERNAL.........................................................10
BRAKE FLUID LEVEL....................................................13
BRAKE PRESSURE SENSOR CIRCUIT.....................................15
BRAKE SWITCH CIRCUIT................................................17
CAB CHECK SUM......................................................21
CAB OPTION...........................................................23
CAN COMMUNICATION ERROR..........................................25
i

TABLE OF CONTENTS - Continued
9.0 CONNECTOR PINOUTS.................................................83
BRAKE FLUID LEVEL SWITCH............................................83
BRAKE LAMP SWITCH C1 (EXCEPT ESP)..................................83
BRAKE LAMP SWITCH C2 (EXCEPT ESP) - BLACK..........................83
CONTROLLER ANTILOCK BRAKE.........................................84
INSTRUMENT CLUSTER C2 - WHITE......................................85
STEERING ANGLE SENSOR..............................................85
TCS SWITCH (ASR) - BLACK.............................................85
WHEEL SPEED SENSOR-LEFT FRONT....................................85
WHEEL SPEED SENSOR-LEFT REAR......................................86
WHEEL SPEED SENSOR-RIGHT FRONT...................................86
WHEEL SPEED SENSOR-RIGHT REAR....................................86
10.0 SCHEMATIC DIAGRAMS.................................................87
10.1BOSCH 5.7 ANTILOCK BRAKE SYSTEM ± ABS.........................87
iii

1.0 INTRODUCTION
The procedures contained in this manual include
all the specifications, instructions, and graphics
needed to diagnose the Sprinter Chassis system
problems: Bosch 5.7 ABS/ESP/TCS (ASR) Braking
System. The diagnostics in this manual are based
on the failure condition or symptom being present
at time of diagnosis.
Please follow the recommendations below when
choosing your diagnostic path.
1. First make sure the DRBIIItis communicating
with the vehicle system being diagnosed. If the
DRBIIItdisplays a ``No Response'' condition, you
must diagnose that first.
2. Read DTC's (diagnostic trouble codes) with the
DRBIIIt.
3. If no DTC's are present, identify the customer
complaint.
4. Once the DTC or customer complaint is iden-
tified locate the matching test in the Table of
Contents and begin to diagnose the system.
All component location views are in Section 8.0.
All connector pinouts are in Section 9.0. All sche-
matics are in Section 10.0.
When repairs are required, refer to the appropri-
ate service manual for the proper removal and
repair procedure.
Diagnostic procedures change every year. New
diagnostic systems may be added; carryover sys-
tems maybe enhanced. READ THIS MANUAL BE-
FORE TRYING TO DIAGNOSE A VEHICLE DI-
AGNOSTIC TROUBLE CODE. It is recommended
that you review the entire manual to become famil-
iar with all new and changed diagnostic procedures.
This manual reflects many suggested changes
from readers of past issues. After using this man-
ual, if you have any comments or recommendations,
please fill out the form at the back of the manual
and mail it back.
1.1 SYSTEM COVERAGE
This diagnostic procedure manual covers the An-
tilock Braking System (ABS), the Electronic Stabil-
ity Program (ESP) and the Traction Control System
(TCS) found on the Sprinter.
1.2 SIX-STEP TROUBLESHOOTING
PROCEDURE
Diagnosis of the Antilock Brake Systems is done
in six basic steps:
²Verification of complaint
²Verification of any related symptoms
²Symptom analysis
²Problem isolation
²Repair of isolated problem
²Verification of proper operation
2.0 INDENTIFICATION OF
SYSTEM
The Bosch 5.7 system can be identified by the 42
way Controller Antilock Brake (CAB), Hydraulic
Control Unit (HCU) and Pump Motor being an
integral electronic/hydraulic unit mounted below
the Master Cylinder with four Wheel Speed Sen-
sors, one at each wheel.
Vehicles with the Traction Control System (TCS/
ASR) can be identified by the presence of the
Traction Control System Switch (TCCS) located on
the center instrument panel.
Vehicles with Electronic Stability Program (ESP)
can be identified by the presence of the Steering
Angle Sensor and the Lateral Acceleration/Yaw
Sensor.
3.0 SYSTEM DESCRIPTION AND
FUNCTIONAL OPERATION
3.1 ESP
The ESP system consists of the electronic control/
hydraulic unit, steering angle sensor, lateral
acceleration/yaw sensor and wheel speed sensors.
When the vehicle is in a turn, the ESP looks at the
steering wheel angle sensor value and monitors the
wheel speed of the inner and outer wheels to ensure
the values are plausible. The steering angle sensor
also measures the speed at which the steering
wheel is turned.
The ESP control module is very similar to the
ABS/ASR module. The ESP is comprised of several
other systems, namely theHBA, ABS, TCS (ASR),
EBDandFZRsystems.
3.2 ABS
The Controller Antilock Brake (CAB) is used to
monitor wheel speeds and modulates (controls) hy-
draulic pressure in each brake channel. The modu-
lated hydraulic pressure is used to prevent wheel
lock up during braking and maintain vehicle stabil-
ity. The CAB also provides a vehicle speed signal
(VSS) to the Electronic Control Module (ECM).
During a non-ABS stop, the system functions as a
standard braking system. The CAB uses special
sortware that monitors the wheel speed(s) and
when certain criteria are met, the software will
1
GENERAL INFORMATION

enable the HCU to perform the brake fluid manage-
ment control as the combination/proportioning
valves.
The Bosch 5.7 system uses the CAB/HCU/Pump
Motor to make an integral electronic/hydraulic unit
which shares data with other electronic modules on
the vehicle via the CAN C Bus network. To access
DTCs from the CAB, the DRBIIItuses the K-ABS
line located in the Data Link Connector (DLC).
3.3 BRAKE ASSIST SYSTEM (HBA)
The Brake Assist System (HBA) analyzes how
hard and fast the driver wants to brake. It monitors
the brake pressure via a pressure sensor. The
passenger car brake assist system uses a vacuum
booster solenoid. The Sprinter uses the hydraulic
control unit to develop the brake pressure.
3.4 TCS (ASR)
The primary function of the Traction Control System
is to reduce wheel slip and maintain traction at the
driven wheels when the road surfaces are slippery. The
Traction Control System reduces wheel slip by applying
the brake that has lost traction. The system is designed
to operate at speeds below 50 km/h (30 mph). The
engine's torque can be reduced by the ECM via the CAN
C Bus, if necessary. The TCS can be deactivated with
switch on the dash. The Traction Control System uses
the ABS to indicate spinning tires to enable the traction
control function. The TCS software is in the CAB.
The TCS (ASR) performs the following functions:
1. Engine power derate
2. Engine deceleration regulation. If the vehicle is
on a patch of ice, the simple action of releasing
the throttle is enough to cause the rear wheels to
slip. To avoid this, the throttle input is regulated
so power drops slowly instead of abruptly. The
engine power is reduced (decelerated) as neces-
sary.
3.5 ELECTRONIC BRAKE DISTRIBUTION
(EBD)
The system was enhanced and eliminates the
need for the ALB system (load sensing valve). All
ESP equipped models will not have ALB. The EBV
system self-adapts to operating conditions. It de-
tects the vehicle's payload when the vehicle starts
and pulls away. Based on the acceleration rate
when the vehicle first pulls away from a standstill,
the system is able to calculate the actual payload.
This is a rough estimate which is used initially.
Later on, the system gathers more precise informa-
tion by monitoring the brake pressure and wheel
speed and negative slip when the driver applies thebrakes. The system will then produce a more accu-
rate calculation of payload depending on brake
retardation. The adaptation is erased when the
ignition is switched off. A new adaptation will occur
on the next driving cycle. By default, the system
acts upon the vehicle as if in an unloaded condition
(safe mode).
Once a new driving cycle begins with the vehicle
in a fully loaded condition (without having gathered
more precise information) the system will detect
ABS actuation in the front wheels and will allow
enough pressure to be applied to the rear axle, to an
extent where the wheels are just about to lock up
(maximum braking possible).
The system calculates the braking force at the
front and rear axles. If the driver applies the brakes
gently and then realizes he needs to apply the
brakes further, the EBV allows the proper pressure
to be applied to the front and rear brakes.
The EBV also contains a feature called ªcorner
brake systemº (CBS) which operates when the ve-
hicle is braked while cornering to avoid a possible
oversteering condition. The EBV monitors the
wheel speed of both rear wheels to detect when the
vehicle is cornering and allows precise brake pres-
sure application to the front and rear brakes. Also
when the brakes are applied during cornering, the
outer wheels get more of the vehicle's weight while
the inner wheels get less weight and could lose
traction (wheel lock up). The EBV system splits the
pressure between left and right sides in addition to
front and rear brakes.
3.6 VEHICLE CONTROLLING (FZR)
Vehicle controlling (FZR)requires additional
sensors to operate. The term ESP refers to the
software of the system. The term FZR refers to the
system controller. The TCS (ASR) system requires
wheel speed sensors to monitor wheel slip and CAN
bus communications to regulate engine power. In
addition to these inputs, the vehicle controlling
(FZR) requires a steering angle sensor, and a lateral
acceleration/yaw rate sensor.
The ESP system does not take the vehicle load
into account. Instead, the coefficient of friction is
calculated in a 20 millisecond period, where the
controller measures the rate at which the wheel
speed is decelerated, as brake pressure is applied to
the wheel.
3.7 SYSTEM COMPONENTS
²Controller Antilock Brake (CAB)
²Hydraulic Control Unit (HCU)
²Pump Motor
2
GENERAL INFORMATION

²Four Wheel Speed Sensors/Tone Wheel assem-
blies
²ABS warning indicator
²TCS (ASR) event indicator
²TCS (ASR) warning indicator
²Steering Angle Sensor
²Lateral Acceleration/Yaw Rate Sensor
²Brake Pressure Sensor
²ESP event indicator
²Brake Fluid Level switch
²Brake Switch (BS)
²Brake Lamp Switch (BLS)
²TCS Switch (TCSS)
²K - ABS
²CAN C Bus
²Fuses, grounds, and wiring
3.7.1 ABS AND TCS (ASR) INDICATORS
This system is equipped with an ABS warning
indicator, TCS (ASR) warning indicator, and TCS
(ASR) event indicator to alert the driver of a
malfunction/event it has detected. The CAB can
request the illumination of the ABS warning indi-
cator, TCS (ASR) warning indicator, and TCS (ASR)
event indicator via CAN C BUS. The CAB controls
the ABS warning indicator by:
²Light steady during an initial test at the begin-
ning of an ignition cycle to function as a bulb
check
²Light steady when a system malfunction exists
(DTC)
²Light steady - If you have not met the speed
required to reset/retest the ABS components
The Instrument Cluster (IC) controls the indica-
tors. The Instrument Cluster transmits a message
over the CAN C Bus relating to diagnostics and
current lamp status for the ABS and TCS (ASR)
indicators. The CAB can control the operation of
TCS warning and TCS event indicators by:
²Both light steady with engine off and both go out
with engine running
²TCS warning indicator lights steady when a TCS
malfunction exists
²TCS event indicator will flash when TCS is in an
active event
3.7.2 CONTROLLER ANTILOCK BRAKE
(CAB)
The CAB is mounted directly to the Hydraulic
Control Unit (HCU) that includes a microprocessor
and twelve solenoids that control valves that con-trol brake pressure during antilock braking or trac-
tion control events. The CAB also has circuits that
monitor the following:
²Double brake switch outputs are monitored to
determine whether or not to prepare for possible
ABS braking
²Wheel Speed Sensors are monitored to determine
when a wheel is tending to lock up. The CAB will
operate the valves in the HCU to control braking
pressure during ABS braking
²Detect ABS system related problems and take
diagnostic action
²Able to execute self-tests and output control com-
mands
When equipped with Electronic Stability (ESP),
the CAB also monitors the following:
²The ESP looks at the Steering Angle Sensor value
and monitors the speed of the inner and outer
wheels to ensure that the values are plausible.
The Steering Angle Sensor also monitors the
speed that the steering wheel is turned.
²The Lateral Acceleration/Yaw Rate Sensor is con-
tained in one unit. The sensor measures side to
side (lateral) motion and rotational motion (how
fast the vehicle is turning).
²The ESP uses data from the Brake Pressure
Sensor to analyze how hard and fast that the
driver wants to brake.
3.7.3 HYDRAULIC CONTROL UNIT (HCU)
The HCU on the Bosch 5.7 has an integral valve
body for controlling the front and rear brakes.
Within the HCU are inlet, outlet, and shuttle
valves, to release brake pressure as required to
avoid wheel lockup, keeping the wheels rolling, and
maintain optimum deceleration with stability. The
Pump Motor is attached to the HCU which works
with the ABS and TCS and is controlled by the
CAB. The primary function is to provide extra
amount of fluid when needed.
3.7.4 SWITCHES/SENSORS
BRAKE SWITCH (BS):This switch prepares the
CAB for a possible antilock event. The CAB uses an
output state voltage from the BS when the brake
pedal is either released/depressed. The Fused Igni-
tion Switch Output circuit supplies 12 volts to the
BS. A released brake pedal will close the BS circuit
and the BS Output circuit supplies 12 volts to the
CAB. When the driver depresses the brake pedal,
the BS Output circuit voltage drops to 0 volts and
the CAB senses the brake pedal state. This tells the
CAB what position the brake pedal is currently in to
make an ABS event possible. When using the
DRBIIItin Inputs/Outputs, the BS and BLS will
3
GENERAL INFORMATION