Description And Operation

DESCRIPTION 

Courtesy of CHRYSLER GROUP, LLC

1. Antilock Brake System (ABS) Module 

OPERATION 

The ABS module is mounted to the Hydraulic Control Unit (HCU) together forming the Integrated Control Unit (ICU). The ABS module is a micro-controller based device which monitors the antilock brake system during normal braking and controls it when the vehicle is in an ABS stop. The ABS function avoids wheels lock during braking maneuvers, maintaining the directionality of the vehicle, and optimizing the reproducibility of stop distance.

The primary functions of the ABS are to:

• Monitor the antilock brake system for proper operation.
• Detect wheel locking or wheel slipping tendencies by monitoring the speed of all four wheels of the vehicle.
• Control fluid modulation to the wheel brakes while the system is in an ABS mode.
• Store diagnostic information.
• Provide communication to the scan tool while in diagnostic mode.
• Illuminate the ABS, ESC, or BRAKE warning indicator lamp when the system is faulted.
• Illuminate the ESC function lamp when a vehicle dynamic event is occurring.
• Provide vehicle speed information, by monitoring the wheel speed sensors, to all modules on the Controller Area Network-Chassis (CAN-C) bus.

The ABS module constantly monitors the antilock brake system for proper operation. If the ABS module detects a fault, it will turn on a warning indicator lamp and disable the antilock braking system. The normal base braking system will remain operational.

The ABS module continuously monitors the speed of each wheel through the signals generated by the wheel speed sensors to determine if any wheel is beginning to lock. When a wheel locking tendency is detected, the ABS module commands the coils to actuate. The coils then open and close the valves in the HCU that modulate brake fluid pressure in some or all of the hydraulic circuits. The ABS module continues to control pressure in individual hydraulic circuits until a locking tendency is no longer present. The ABS module contains a self-diagnostic program that monitors the antilock brake system for system faults. When a fault is detected, a warning indicator lamp is turned on and the fault Diagnostic Trouble Code (DTC) is then stored in a diagnostic program memory. A latched fault will disable certain system functionality for the current ignition cycle. An unlatched fault will disable certain system functionality until the fault condition disappears. These DTCs will remain in the ABS module memory even after the ignition has been turned off. The DTCs can be read and cleared from the ABS module memory by a technician using a scan tool. If not cleared with a scan tool, the fault occurrence and DTC will be automatically cleared from the ABS module memory after the identical fault has not been seen during the next 100 ignition cycles may be required for the amber ABS warning indicator lamp to extinguish on the next ignition cycle.

The ABS module covers ABS braking functions, Cornering Brake Control (CBC), Drag Torque Control Motor [Schleppmomenten Regelung] (MSR), and Off-Road ABS (ORA) ESC functions.

The ESC:

• Attempts to avoid wheel lock for ABS operation
• Reduces oversteer tendencies for CBC operation
• Attempts to avoid drive axle locking for MSR operation
• Optimally decelerate off-road for ORA operation

Electric Parking Brake (EPB) 

The EPB function occurs in the ABS module. The ABS module receives a hardwired input from the EPB switch when actuated by the driver. The ABS module receives EPB command through CAN bus. The ABS module uses a hardwired connection to control the EPB Light Emitting Diode (LED) indicator. The ABS module will perform dynamic braking either by ESC function or EPB functions. The module will also perform a conditions check and control the motors on calipers to engage or disengage park brake.

The purpose of the EPB is to replace the traditional manually operated park brake hardware in a vehicle. It replaces the traditional manually pulled lever system pulling a cable attached to the brake by using an electronic switch and computer controlled electronic actuator fixed to the brake caliper. The system provides a number of safety functions, designed to protect the vehicle and pedestrians, or as degraded modes of operation designed to keep the vehicle operational after fault.

In addition to manually applying and releasing the park brake on the driver's command the EPB system also has a number of features that assist the driver to obtain extra comfortable driving experience.