Description And Operation: Operation

The primary functions of the ABS module 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 diagnostic scan tool while in diagnostic mode.
• Illuminate the ABS, ESC, or EPB warning indicator lamp when the system is faulted.
• Illuminate the ABS, ESC, or EPB function lamp when a vehicle dynamic event is occurring.
• Illuminate the electric park brake warning lamp when a malfunction is present
• Control the EPB functions

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 ABS command 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 diagnostic scan tool. If not cleared with a diagnostic 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 3, 500 miles. Drive-off may be required for the amber ABS warning indicator lamp to go out on the next ignition cycle.

The ABS module receives 12 volt constant power and 12 volt key ON ignition signal power. It controls the ON/OFF output command for the EPB actuators, the electromechanical motor gear unit that drives both rear brake caliper pistons during park brake mode.

Input to the ABS module for the ON/OFF action is received from the EPB manual switch and the Controller Area Network - Chassis (CAN C) data bus from the Electronic Vehicle Information Center (EVIC), Radio Receiver Module (RRM) touchscreen, Electronic Stability Control (ESC), and other controllers including the diagnostic scan tool (for Service Mode).

The output of the module is controlled by the following conditions:

Manual Apply 

• The ABS module will apply the parking brakes when the EPB switch is pulled and the vehicle is at a stop (ignition ON or OFF). The ABS module can also apply the brakes while the vehicle is moving if the EPB switch is pulled to request a dynamic apply, where hydraulic braking is actuated via the ESC system.

Manual Release 

• The ABS module will release the EPB when the EPB switch is pushed, the brake pedal is applied with the driver seat belt  buckled and the ignition ON.

Auto Park Brake 

• The EPB will apply when the transmission is moved into the PARK position or whenever the ignition is turned OFF with a manual transmission. This occurs when the driver selects this option from the RRM touchscreen menu which commands the ABS module to apply the EPB.

Drive Away Release 

• When in any drive gear, the ABS module will automatically release the EPB when throttle input and engine torque is detected.

Safe Hold 

• If the ABS module detects that the vehicle is not secure (transmission not in PARK, door open, and others), it will actuate the EPB. This is hard programmed into the module and is not able to be turned OFF.

Loss of Voltage 

• The ABS module is not able to manually release EPB when voltage is lost.

External Apply 

• Other vehicle systems can request the ABS module to apply the EPB if necessary to secure the vehicle.

Service Mode 

• The ABS module can be commanded to retract the EPB actuators through the RRM touchscreen (customer usable method) and through the diagnostic scan tool.
  NOTE:

  The EPB fault light flashes continuously in Service Mode. Actuating the EPB switch will remove the vehicle from Service Mode. 

The EPB switch can be actuated at any time. Depending on the speed of the vehicle when the EPB switch is actuated, the ABS module will output different commands under the following conditions:

Static Apply  (under 5 km/h [3 mph]) - Actuates the EPB motors attached to the rear calipers.

Dynamic Apply  (over 5 km/h [3 mph]) - Actuates the hydraulic braking system.

The ABS module fail-safe includes that the EPB can be applied with the ignition OFF, the EPB cannot be released with the ignition OFF, and the brake pedal must be applied with the driver seat belt  buckled when releasing the EPB.

Courtesy of CHRYSLER GROUP, LLC

The ABS module illuminates the red BRAKE warning lamp when EPB is applied. ABS module faults are indicated through the amber EPB fault lamp and EVIC messages when present.