FREE REPAIR MANUALS & LABOR GUIDES 1982-2013 Vehicles
Courtesy of Operation CHARM: Car repair manuals for everyone.
Home >> Ford Truck >> 2012 >> Explorer FWD L4-2.0L Turbo >> Repair and Diagnosis >> Brakes and Traction Control >> Antilock Brakes / Traction Control Systems >> Description and Operation >> System Operation >> Part 2

Part 2




Anti-Lock Brake System (ABS) And Stability Control

System Operation

Hill Start Assist

The ABS (Anti-Lock Brake System) module uses the brake pedal switch message and ABS (Anti-Lock Brake System) wheel speed sensor input to determine that the vehicle is at a complete stop. The transmission selector lever message and parking brake message let the ABS (Anti-Lock Brake System) module know that the vehicle is not being parked. The stability sensor messages from the RCM (Restraints Control Module) enable the ABS (Anti-Lock Brake System) module to determine if the vehicle is on an incline greater than 5 degrees or greater than a 3% grade. The hill start assist function automatically engages once the above conditions have been met. As the driver releases the brake pedal, the ABS (Anti-Lock Brake System) module commands the HCU (Hydraulic Control Unit) to close the isolation valves which will maintain the current brake system pressure, preventing the vehicle from rolling down the incline. The ABS (Anti-Lock Brake System) will hold the brake pressure for up to 2 seconds while the driver transitions to the accelerator pedal. As the accelerator pedal is pressed and the engine RPM (Revolutions Per Minute) increases, the ABS (Anti-Lock Brake System) module gradually releases the brake pressure to make sure the vehicle is neither rolling back nor driving off until there is sufficient driving torque to accelerate the vehicle forward (or backward if reversing up the incline).

MyKey(R) Interaction

Through the MyKey(R) feature, the traction control function of the vehicle dynamic system can be configured to be always on or to allow the driver to select the traction control function on or off.
When the traction control function is configured to be always on and a MyKey(R) restricted key is in use, the IPC (Instrument Panel Cluster) will ignore any requests made by the driver to disable the traction control function and will not send any traction control disable messages to the ABS (Anti-Lock Brake System) module. Refer to the Owner's Literature.

Terrain Management

The ABS (Anti-Lock Brake System) module adjusts the vehicle dynamic system operational parameters when the terrain mode request message is received from the ATCM (All Terrain Control Module), depending on the terrain mode requested.
- Grass/Gravel/Snow - The base ABS (Anti-Lock Brake System), traction control and ESC (Electronic Stability Control) lower the threshold used to detect wheel lock up as it is more likely to occur on loose, slippery surfaces.

Sand - The base ABS (Anti-Lock Brake System) raises the threshold used to detect wheel lock up to allow the vehicle to" dig into" sand or deep gravel surfaces. Traction control and ESC (Electronic Stability Control) raise the parameters for brake and engine torque reductions to optimize traction and engine performance.
Mud/Ruts- The base ABS (Anti-Lock Brake System) lowers the threshold used to detect wheel lock up as it is more likely to occur on slippery, muddy surfaces. Traction control and ESC (Electronic Stability Control) raises the parameters for brake and engine torque reductions to optimize traction and engine performance.
For additional information on the terrain management system, REFER to All-Wheel Drive (AWD) .

Hill Descent Control

When the Hill Descent Control(TM) switch is pressed, the ATCM (All Terrain Control Module) sends a message to the ABS (Anti-Lock Brake System) module requesting hill descent braking assist. Once the vehicle speed is between 5 km/h (3.1 mph) and 32 km/h (19.9 mph) and the transmission is in REVERSE or any forward gear, the ABS (Anti-Lock Brake System) module uses the hydraulic pump motor and the HCU (Hydraulic Control Unit) solenoid valves to maintain the vehicle speed set by the driver. If the vehicle speed is increased or decreased outside of the operational window, the system remains active but descent speed cannot be set or maintained.
The Hill Descent Control(TM) system requires a cool down period after sustained use. The ABS (Anti-Lock Brake System) module continually monitors the descent speed, angle of descent, pump motor run time and solenoid valve use. Once the ABS (Anti-Lock Brake System) module determines that a cool down period is needed, the ABS (Anti-Lock Brake System) module sends a message to the BCM (Body Control Module) and the IPC (Instrument Panel Cluster) over the HS-CAN (High Speed Controller Area Network) to alert the driver via a message center message that the system requires a cool down period.

Trailer Sway Control

Trailer sway control is a unique function of the vehicle dynamic system that uses steering wheel angle information from the SCCM (Steering Column Control Module) (vehicles with active park assist) or from the PSCM (Power Steering Control Module) (vehicles without active park assist) and the yaw information from the RCM (Restraints Control Module) to determine if a trailer sway event is taking place. Trailer sway is the undesirable yaw force a trailer can apply to the towing vehicle. If it is determined that an event is taking place, the ABS (Anti-Lock Brake System) module modulates brake pressure to the appropriate brake caliper(s) by opening and closing the appropriate solenoid valves inside the HCU (Hydraulic Control Unit) while the hydraulic pump motor is activated. At the same time, the ABS (Anti-Lock Brake System) module sends a message over the HS-CAN (High Speed Controller Area Network) that a trailer sway event is taking place. When the PCM (Powertrain Control Module) receives this message, it assists with trailer sway control by adjusting engine timing and decreasing fuel injector pulses. When the IPC (Instrument Panel Cluster) receives this message, it flashes the stability/traction control indicator (sliding car icon) and displays TRAILER SWAY, REDUCE SPEED in the message center. Once the trailer sway has been corrected, the ABS (Anti-Lock Brake System) module returns the solenoid valves in the HCU (Hydraulic Control Unit) to their normal position, deactivates the hydraulic pump motor and sends another message over the HS-CAN (High Speed Controller Area Network) bus indicating that the event has ended. The PCM (Powertrain Control Module) returns engine timing and fuel injectors to normal operation and the IPC (Instrument Panel Cluster) extinguishes the sliding car icon.
Trailer sway control only activates when vehicle speed is greater than 65 km/h (40.4 mph). Any malfunction that disables the RSC (Roll Stability Control) function of the vehicle dynamic system also disables trailer sway control. Trailer sway control can also be disabled by the driver through the menu in the message center. Regardless of the chosen state (enabled or disabled) set by the driver, trailer sway control is enabled at each ignition key cycle.

Stability-Traction Control Indicator (Sliding Car Icon)

REFER to Stability-Traction Control Indicator (Sliding Car Icon) .

Stability-Traction Control Disabled Indicator (Sliding Car OFF Icon)

REFER to Stability-Traction Control Disabled Indicator (Sliding Car OFF Icon) .

Curve Control

The ABS (Anti-Lock Brake System) module continuously monitors the vehicle motion relative to the intended course. This is done by using sensors to compare the steering wheel input, the yaw rate sensor input, the lateral acceleration sensor input and the longitudinal acceleration sensor input with that of the actual vehicle motion. The SCCM (Steering Column Control Module) (vehicles with active park assist) or PSCM (Power Steering Control Module) (vehicles without active park assist) sends the steering wheel angle and rate of change information to the ABS (Anti-Lock Brake System) module over the HS-CAN (High Speed Controller Area Network) while the RCM (Restraints Control Module) sends the yaw rate, lateral acceleration and longitudinal acceleration sensor information to the ABS (Anti-Lock Brake System) module over a private HS-CAN (High Speed Controller Area Network). If the ABS (Anti-Lock Brake System) module determines from the inputs that the vehicle is experiencing over-steer or under-steer, the module sends a message over the HS-CAN (High Speed Controller Area Network) that a curve control event is taking place. When the PCM (Powertrain Control Module) receives this message, it assists with curve control by adjusting engine timing and decreasing fuel injector pulses. When the IPC (Instrument Panel Cluster) receives this message, it flashes the stability/traction control indicator (sliding car icon). The ABS (Anti-Lock Brake System) module continues to monitor the sensor inputs while the PCM (Powertrain Control Module) assists with curve control. If the ABS (Anti-Lock Brake System) module determines that PCM (Powertrain Control Module) intervention is insufficient to control the stability event, the ABS (Anti-Lock Brake System) module modulates brake pressure to the appropriate brake caliper(s) by opening and closing the appropriate solenoid valves inside the HCU (Hydraulic Control Unit) while the hydraulic pump motor is activated. Once the vehicle instability has been corrected, the ABS (Anti-Lock Brake System) module returns the solenoid valves in the HCU (Hydraulic Control Unit) to their normal position, deactivates the hydraulic pump motor and sends another message over the HS-CAN (High Speed Controller Area Network) bus indicating that the event has ended. The PCM (Powertrain Control Module) returns engine timing and fuel injectors to normal operation and the IPC (Instrument Panel Cluster) extinguishes the sliding car icon.
The Curve Control function does not operate with the transmission in REVERSE. The ABS (Anti-Lock Brake System) module disables the Curve Control function if there are any wheel speed sensor, stability sensor or steering angle sensor DTCs (Diagnostic Trouble Codes) present in the ABS (Anti-Lock Brake System) module. Also, if there is a communication error between the ABS (Anti-Lock Brake System) module and the PSCM (Power Steering Control Module), the SCCM (Steering Column Control Module) or the RCM (Restraints Control Module) the Curve Control function is disabled. When the Curve Control function is disabled, the ABS (Anti-Lock Brake System) module sends a message over the HS-CAN (High Speed Controller Area Network) to the IPC (Instrument Panel Cluster) to illuminate both the sliding car icon and the stability/traction control disabled indicator (sliding car OFF icon).

Supplemental Braking Assist

In addition to preventing wheel lock up during braking events, the ABS (Anti-Lock Brake System) module is also able to provide supplemental hydraulic brake assist through the use of the hydraulic pump motor and the HCU (Hydraulic Control Unit). This is done in the event of a severe vacuum loss at the brake booster, to maintain the distance gap set by the adaptive cruise control system or to aid in the avoidance of forward collisions.
The ABS (Anti-Lock Brake System) module utilizes the HCU (Hydraulic Control Unit) and hydraulic pump motor to aid in bringing the vehicle to a safe, controlled stop in the event of severe vacuum loss at the brake booster. The ABS (Anti-Lock Brake System) module continually monitors the vacuum in the brake booster through the use of a vacuum sensor. When the vacuum sensor indicates vacuum is below a predetermined level, a DTC (Diagnostic Trouble Code) is set in the ABS (Anti-Lock Brake System) module. If this occurs during a braking event or if the driver attempts to stop the vehicle with a low vacuum condition in the brake booster, the ABS (Anti-Lock Brake System) module activates the hydraulic pump motor in the HCU (Hydraulic Control Unit) to assist with vehicle braking.
On vehicles equipped with adaptive cruise control, the C-CM (Cruise-Control Module) monitors the area forward of the vehicle. When an object enters this area and closes the distance gap set by the driver, the C-CM (Cruise-Control Module) sends a deceleration request to the ABS (Anti-Lock Brake System) module over the HS-CAN (High Speed Controller Area Network) (either an adaptive cruise control deceleration request or a collision avoidance deceleration request). When the deceleration request message is received, the ABS (Anti-Lock Brake System) module activates the hydraulic pump motor and solenoid valves in the HCU (Hydraulic Control Unit) to slow the vehicle down to maintain the distance gap set by the driver. Once the distance gap set by the driver is achieved, the C-CM (Cruise-Control Module) stops sending the deceleration request message and the ABS (Anti-Lock Brake System) module deactivates the hydraulic pump motor and solenoid valves in the HCU (Hydraulic Control Unit). If the C-CM (Cruise-Control Module) determines that the amount of braking provided by the ABS (Anti-Lock Brake System) module is insufficient, the C-CM (Cruise-Control Module) sends a forward collision avoidance braking request message to the ABS (Anti-Lock Brake System) module and warns the driver, both audibly and visually, through the use of the HUD (Head Up Display). After receiving the braking request message, the ABS (Anti-Lock Brake System) module waits for brake pedal input and at that time applies maximum braking assist using the hydraulic pump motor and the HCU (Hydraulic Control Unit). For additional information on the adaptive cruise control system, REFER to Adaptive Cruise Control (ACC) Operation . For additional information on the collision avoidance system, REFER to Collision Avoidance Operation .
pro multis Credits:Operation CHARM About Operation CHARM