Ford Explorer: Parking Brake and Actuation / Description and Operation - Parking Brake - System Operation and Component Description

System Operation

System Diagram

E338887 *.sttxt { visibility: hidden; } *.stcallout { visibility: visible; } 1 Parking Brake Control Switch 2 LH Parking Brake Actuator Motor 3 RH Parking Brake Actuator Motor 4 PCM 5 GSM 6 RCM 7 BCM 8 GWM 9 IPC 10 ABS HS-CAN 2 HS-CAN 1 FD-CAN HS-CAN 3

Item	Description
1	Parking Brake Control Switch
2	LH Parking Brake Actuator Motor
3	RH Parking Brake Actuator Motor
4	PCM
5	GSM
6	RCM
7	BCM
8	GWM
9	IPC
10	ABS

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Network Message Chart

  ABS Module Electronic Parking Brake Network Input Messages

Broadcast Message	Originating Module	Message Purpose
Accelerator pedal position	PCM	This message is sent to the GWM and then to the ABS module. This message informs the ABS module of the current position of the accelerator pedal, 0-100%.
Brake pedal applied	PCM	This message is sent to the GWM and then to the ABS module. This message informs the ABS module the driver has pressed the brake pedal.
Driven wheel propulsion torque	PCM	This message is sent to the GWM and then to the ABS module. This message provides the ABS module of the current amount of propelling torque being applied to the driven wheels by the engine or electric motor.
Driver door ajar status	BCM	This message is sent to the GWM and then to the ABS module. This message informs the ABS module the driver door status, closed or open.
Driver seat belt buckle status	RCM	This message informs the ABS module of the current status of the driver seat belt buckle; belted, unbelted, faulty or unknown.
Engine RPM	PCM	This message is sent to the GWM and then to the ABS module. This message informs the ABS module of the current engine RPM.
Gear lever position	PCM	This message is sent to the GWM and then to the ABS module. This message informs the ABS module of the current gear selector lever position.
Ignition status	BCM	This message is sent to the GWM and then to the ABS module. This message informs the ABS module of the current ignition status; off, accessory, run, start, invalid or unknown.
Longitudinal acceleration	RCM	The ABS module uses this message to confirm forward or rearward vehicle movement.
Transmission in REVERSE	PCM	This message is sent to the GWM and then to the ABS module. This message informs the ABS module of the current reverse gear status; inactive or active.
Vehicle configuration data	BCM	This message is sent to the GWM and then to the ABS module. This message provides the ABS module with the current optional and configured items such as tire size, axle ratio, keyless entry and VIN.

Parking Brake and Actuation

The ABS module monitors and controls the parking brake system. The ABS module sends a reference voltage to the parking brake switch. When the driver moves the parking brake switch to the APPLY position, the reference voltage is sent back to the ABS module indicating an APPLY request. The ABS module then determines from sensor inputs if the parking brakes can be applied and sends voltage to the parking brake actuator motors. Once the parking brakes are fully applied, the ABS module sends a message to the IPC which illuminates the red BRAKE warning indicator. If the red BRAKE warning indicator is already illuminated due to a non-parking brake concern, the IPC displays PARK BRAKE APPLIED in the message center. When the driver moves the parking brake switch to the RELEASE position, the reference voltage is sent back to the ABS module indicating a RELEASE request. The ABS module then determines from sensor inputs and CAN messages (ignition state and brake pedal input) if the parking brakes can be released and sends voltage to the parking brake actuator motors. Once the parking brakes are fully released, the ABS module sends a message to the IPC which extinguishes the red BRAKE warning indicator. If the red BRAKE warning indicator cannot be extinguished due to a non-parking brake concern, the IPC displays PARK BRAKE RELEASED in the message center.

Automatic Release

The parking brake is designed to automatically release under the following circumstances:

• the driver door must be closed.
• the driver safety belt must be fastened (vehicles built before July 2015).
• the engine must be running.
• the transmission must be in any forward gear or REVERSE.

Once all the conditions have been met, the parking brake releases automatically when the accelerator pedal is pressed. A vehicle driving away up an incline requires more accelerator pedal input than a vehicle driving away down an incline.

Service Mode

Service mode is also known as maintenance mode. The parking brake system must be placed in service mode to service the rear brake pads or when removing rear brake components to service other components. The system can be placed in service mode by using the diagnostic scan tool or by following the steps in the EPB Service Mode Activation and Deactivation procedure.
Refer to: Electronic Parking Brake (EPB) Service Mode Activation and Deactivation (206-05) .

Once the system is placed in service mode, the message center will display MAINTENANCE MODE, the yellow parking brake indicator illuminates and the parking brake system is deactivated. The only way to reactivate the parking brake system is by correctly exiting service mode. Disconnecting the vehicle battery will not reset the system or exit service mode. If the vehicle is driven greater than 8 km/h (5 mph) while in service mode, the yellow parking brake warning indicator is illuminated, the red BRAKE warning indicator flashes and a warning chime sounds.

Red Brake Warning Indicator

The red BRAKE warning indicator notifies the driver of hydraulic brake concerns, some ABS concerns and parking brake application. When a hydraulic brake or ABS concern is present, the warning indicator illuminates solidly. After the parking brakes are fully applied, the red BRAKE warning indicator illuminates and remains illuminated as long as the ignition is set to ON. If the ignition is set to OFF after the parking brakes are applied or if the parking brakes are applied after the ignition is set to OFF the red BRAKE warning indicator illuminates for 10 seconds and is then extinguished.
Refer to: Instrument Panel Cluster (IPC) - System Operation and Component Description (413-01 Instrumentation, Message Center and Warning Chimes, Description and Operation).

Yellow Parking Brake Indicator

The yellow parking brake indicator is used in conjunction with the message center to notify the driver of parking brake system concerns. When a concern or DTC is present, the indicator illuminates and a message is displayed in the message center. The yellow parking brake indicator also illuminates when the parking brake system is in service mode.
Refer to: Instrument Panel Cluster (IPC) - System Operation and Component Description (413-01 Instrumentation, Message Center and Warning Chimes, Description and Operation).

Component Description

Anti-Lock Brake System (ABS) Module

The ABS module is attached directly to the HCU and is the electronic control unit for the parking brake system. The ABS module monitors all switch inputs, sensor inputs and HS-CAN messages relating to the parking brake system, then directly controls the parking brake actuator motors. The ABS module also sets Diagnostic Trouble Codes (DTCs) in the event that a system or component failure should occur.
Refer to: Anti-Lock Brake System (ABS) and Stability Control (206-09 Anti-Lock Brake System (ABS) and Stability Control, Diagnosis and Testing).

Parking Brake Actuator Motor

The parking brake actuator motors are single speed reversible electric motors mounted on the rear brake calipers. The motors can be serviced separately from the calipers.

Parking Brake Switch

The parking brake switch is a 3 position switch with 2 sets of 3 internal micro switches, one set is for APPLY and one set is for RELEASE. The 3 switch positions are APPLY (pulled up), NEUTRAL (at rest or static) and RELEASE (pushed down).

Whenever the parking brake switch is disconnected and then reconnected, a DTC sets in the ABS module and the ABS module disables the parking brake system. To restore parking brake system functionality and to clear the DTC, the parking brake switch must be moved through all 3 positions twice within 5 seconds pausing for approximately one-half second when the switch is in the NEUTRAL position between each apply and release.