Sprinter 3500 L5-2.7L DSL Turbo (2004)
Electronic Brake Control Module: Description and Operation
SYSTEM COMPONENTS
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Controller Antilock Brake (CAB)
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Hydraulic Control Unit (HCU)
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Pump Motor
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Four Wheel Speed Sensors/Tone Wheel assemblies
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ABS warning indicator
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TCS (ASR) event indicator
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TCS (ASR) warning indicator Steering Angle Sensor
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Lateral Acceleration/Yaw Rate Sensor
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Brake Pressure Sensor
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ESP event indicator
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Brake Fluid Level switch
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Brake Switch (BS)
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Brake Lamp Switch (BLS)
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TCS Switch (TCSS)
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K - ABS
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CAN C Bus
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Fuses, grounds, and wiring
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 indicator, TCS (ASR) warning indicator, and TCS
(ASR) event indicator via CAN C BUS. The CAB controls the ABS warning indicator by:
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Light steady during an initial test at the beginning of an ignition cycle to function as a bulb check
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Light steady when a system malfunction exists (DTC)
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Light steady - If you have not met the speed required to reset/retest the ABS components
The Instrument Cluster (IC) controls the indicators. 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:
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Both light steady with engine off and both go out with engine running
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TCS warning indicator lights steady when a TCS malfunction exists
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TCS event indicator will flash when TCS is in an active event
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
control brake pressure during antilock braking or traction control events. The CAB also has circuits that monitor the following:
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Double brake switch outputs are monitored to determine whether or not to prepare for possible ABS braking
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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
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Detect ABS system related problems and take diagnostic action
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Able to execute self tests and output control commands
When equipped with Electronic Stability (ESP), the CAB also monitors the following:
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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.
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The Lateral Acceleration/Yaw Rate Sensor is contained in one unit. The sensor measures side to side (lateral) motion and rotational motion (how
fast the vehicle is turning).
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The ESP uses data from the Brake Pressure Sensor to analyze how hard and fast that the driver wants to brake.
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.
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 Ignition 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 in Inputs/Outputs, the BS and BLS will read opposite switch states. Note: The BS and BLS are in the same switch housing.
BRAKE LAMP SWITCH (BLS): This switch prepares the CAB for a possible antilock event. The CAB uses an output state voltage from the BLS
when the brake pedal is either depressed/released. The Fused Ignition Switch Output circuit supplies 12 volts to the BLS. A depressed brake pedal will
