•
Four Wheel Speed Sensors/Tone Wheel assem-
blies
•
ABS warning indicator
•
TCS (ASR) event indicator
•
TCS (ASR) warning indicator
•
Steering Angle Sensor
•
Lateral Acceleration/Yaw Rate Sensor
•
Brake Pressure Sensor
•
ESP event indicator
•
Brake Fluid Level switch
•
Brake Switch (BS)
•
Brake Lamp Switch (BLS)
•
TCS Switch (TCSS)
•
K - ABS
•
CAN C Bus
•
Fuses, 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:
•
Light steady during an initial test at the begin-
ning of an ignition cycle to function as a bulb
check
•
Light steady when a system malfunction exists
(DTC)
•
Light 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:
•
Both light steady with engine off and both go out
with engine running
•
TCS warning indicator lights steady when a TCS
malfunction exists
•
TCS 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:
•
Double brake switch outputs are monitored to
determine whether or not to prepare for possible
ABS braking
•
Wheel 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
•
Detect ABS system related problems and take
diagnostic action
•
Able to execute self-tests and output control com-
mands
When equipped with Electronic Stability (ESP),
the CAB also monitors the following:
•
The 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.
•
The 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).
•
The 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
DRBIII
t in Inputs/Outputs, the BS and BLS will
3
GENERAL INFORMATION