Description And Operation
DESCRIPTION
The Antilock Brake System (ABS) module (1) is mounted to the Hydraulic Control Unit (HCU) (2) as part of the Integrated Control Unit (ICU). The ICU is located in the engine compartment on the driver side underneath the cowl panel. For information on the ICU. Refer to DESCRIPTION AND OPERATION .
OPERATION
ABS Module Functions
- Active Yaw Control (AYC) - The AYC uses the brakes of each wheel to stabilize the vehicle during braking with the two wheels on one side on one type of road (e.g. wet streets) and the wheels on the other side on another type (for example, dry streets).
- Adaptive Brake Light (ABL) - The ABL identifies the braking pressure present and activates the brake lights with varying intensity.
- Antilock Brake System (ABS) - The ABS prevents the wheels from locking up under hard braking conditions.
- Auto Hazard Warning(AHW) - The AHW system identifies braking situations and activates the hazard lights.
- Autonomous Emergency Braking (AEB) - The AEB intervenes when an external module identifies and requires the braking system intervention.
- Driver Steering Recommendation (DSR) - In combination with the Electric Power Steering (EPS), the driver steering recommendation function can give the driver suggestions on how to set the steering wheel angle to increase vehicle stability.
- Dynamic Brake Function (DBF) - The DBF decelerates the moving vehicle to a stop when the switch of the Electric Parking Brake (EPB) is activated. The EPB operation starts when the vehicle speed is near 0 km/h (0 mph). After the vehicle has stopped and the EPB is active, the hydraulic pressure is released.
- Dynamic Torque Vectoring (DTV) - Controls the Alfa™ Active Torque Vectoring differential to improve the agility and handling of the vehicle.
- Electric Parking Brake (EPB) - The EPB replaces the parking brakes manual operation with an electromechanical system. The replacement of the parking brake lever with a switch offers extra space in the passenger compartment permitting additional features.
- Electronic Stability Control (ESC) - The ESC uses the braking of each wheel to stabilize the vehicle movement.
- Electronic Brake Assist (EBA) - The purpose of the EBA, is to measure how quickly the driver presses the brake pedal. Based on the brake pedal application speed and pressure, the system recognizes if the driver wants to apply a braking force and promptly provides the maximum braking pressure.
- Electronic Brake Force Distribution (EBD) - The EBD system adjusts the braking pressure on the rear axle to prevent locking that could destabilize the behavior of the vehicle during braking.
- Engine Drag Control - The engine drag control prevents the drive wheels from locking during downshifts based on anticipations, throttle control (slightly opening) and waste gate.
- Engine Traction Control System (ETCS) - The ETCS prevents slippage of the drive wheels during acceleration, reducing engine torque to stabilize the vehicle.
- Enhanced Stability Braking System (ESBS) - This is an advanced function of the ABS that improves and optimizes the stability and maneuverability of driving during ABS braking events on curves.
- Hill Start Assist (HSA) - HSA helps the vehicle operator keep the vehicle stopped while placing in gear when starting the vehicle on inclines.
- Maximum Brake Support (MBS) - The maximum brake support activates the ABS function on the rear axle even if the brake pressure has not reached a high value.
- Panic Brake Assist (PBA) - The PBA helps the driver to achieve maximum braking pressure during emergency braking situations.
- Rain Brake Assist (RBA) - The RBA is activated when the windshield wipers are active. This function gently applies the brake pads to remove water from the surface of the brake rotor.
- Ready Alert Brake - Ready alert braking eliminates the air gap between the pads and rotors.
- Rollover Stability Control (RSC) - The RSC is designed to reduce the risk of rollover of the vehicle.
- Traction Control (TC) - Traction Control prevents excessive drive wheel slip.
- Vehicle Dive Limiter - This pitch limitation function limits the speed at which the nose of the vehicle tends to rise again after heavy braking.
Additional detail
The ABS module must manage all the effects caused by the lowering of tension due to the absorption by the electronic components of the vehicle and to the lowering of tension due to starting of the engine.
Besides such absorption it must manage any voltage overloads in order to prevent braking system malfunctions.
Diagnostic Trouble Code (DTC)s are stored in the ABS module and specific warning indicator lamps will be illuminated on the Instrument Panel Cluster (IPC) to alert the operator of potential issues.
Due to the design and operating characteristics of the ABS module, the driver could experience a different response from the brake pedal between engine off and engine on conditions. This is a characteristic of the system itself. The braking pressure is not created in any way from the pedal but from an electric motor, a mechanical actuator and integrated electronics in the ABS module.
The feel of the brake pedal varies with the position of the Dynamic, Natural, Advanced Efficiency (DNA) driving selector, less reactive in Natural and Advanced Efficiency diving modes, more reactive in the Dynamic and Race modes.
If the brake fluid must be changed, the system must be purged normally. If, for any reason, the system or the ABS module is emptied, the dedicated bleed procedure must be performed by using the diagnostic scan tool.
If the ABS module is replaced during servicing, the new module is already supplied with the correct amount of brake fluid. Perform the traditional brake bleeding procedure once the module has been replaced.
The traditional brake bleeding procedure must be performed when the braking system is in the fallback recovery operating condition.
The system can be forced to enter the fallback recovery condition in two ways:
- Launching a specific routine using the diagnostic scan tool.
- Disconnecting the battery.
ABS module operating logic
The ICU continuously performs tests to know the operating state of the entire braking system.
The ICU monitors the pressures by using sensors and processes the amount of brake fluid volume used by the braking system to determine possible lose of pressure in the hydraulic circuits and evaluate the correct operation of the master cylinder and the actuator.
If a pressure leak is found in a hydraulic circuit, the system is able to isolate it and bypass it, keeping the other hydraulic circuit in operation.
The hydraulic circuits of the braking system are two isolated and independent circuits from each other; they correspond to:
- The primary hydraulic circuit: supplies brake fluid to the left front caliper and the right rear caliper.
- The secondary hydraulic circuit: supplies brake fluid to the front right caliper and the left rear caliper.
The braking system can operate according to two distinct modes:
- Normal operating function (brake by wire)
- Recovery operation (fallback)
Following are the symbols with related explanations to help in understanding the functioning of the system:
- (1) Vehicle unlocking
- (2) Door opening
- (3) Ignition and Start
- (4) Brake pedal applied
- (5) Brake pedal released
- (6) Electric brake available / Electric brake not available
- (7) Dynamic Control functions available or Dynamic Control functions not available
- (8) Brake failure warning lamp ON / Brake failure warning lamp OFF
- (9) ABS failure warning lamp ON / ABS failure warning lamp OFF
- (10) ESC failure warning lamp ON / ESC failure warning lamp OFF