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Home >> Lincoln >> 2011 >> MKT AWD V6-3.7L >> Repair and Diagnosis >> Brakes and Traction Control >> Antilock Brakes / Traction Control Systems >> Description and Operation
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Antilock Brakes / Traction Control Systems: Description and Operation




Anti-Lock Control

ABS With Traction Control, Electronic Stability Control (ESC) and Roll Stability Control (RSC(R))

The ABS with traction control, Electronic Stability Control (ESC) and Roll Stability Control (RSC(R)) consists of the following components:

- ABS module - attached to the Hydraulic Control Unit (HCU), but can be serviced separately.
- Front wheel speed sensors - one sensor is located in each front wheel knuckle. The sensors are serviced separately from the knuckle.
- Front wheel speed sensor tone rings - one tone ring is located in each wheel bearing and wheel hub assembly and is serviced with the wheel bearing and wheel hub.
- HCU - which contains several valves (inlet and outlet), the hydraulic pump motor and is mounted behind the battery and battery tray.
- Rear wheel speed sensors - one sensor is located in each rear wheel knuckle, the sensors are serviced separately from the knuckle.
- Rear wheel speed sensor tone rings - one tone ring is located in each wheel bearing and wheel hub assembly and is serviced with the wheel bearing and wheel hub.
- Stability control sensors - located inside of the Restraints Control Module (RCM) and consists of the following sensors: yaw rate, roll rate, lateral accelerometer and longitudinal accelerometer. The sensors are integral to the RCM and cannot be serviced separately.
- Steering Angle Sensor Module (SASM) - vehicles that are equipped with Electronic Power Assist Steering (EPAS), but without the Active Park Assist feature have a SASM which does not have any electrical components inside. It is only installed to provide structural support for the clockspring and for turn signal canceling. On these vehicles, the steering wheel rotation and angle information (an input for Roll Stability Control (RSC(R)), Trailer Sway Control and Active Park Assist functions) is sent from the Power Steering Control Module (PSCM). Vehicles with the Active Park Assist feature have a fully functional SASM and also receive steering wheel information from the PSCM.
- Steering wheel rotation sensor, vehicles with Hydraulic Power Assist Steering (HPAS) only - located on the RH side of the clockspring and is serviced separately from the clockspring assembly. The sensor provides steering rotation information to facilitate RSC(R) and Trailer Sway Control functions.
- Steering wheel rotation sensor ring, vehicles with HPAS only - located on the clockspring and is serviced with the clockspring assembly.
- Traction control switch - located in the Front Controls Interface Module (FCIM) and is serviced with the FCIM.

Electronic Brake Distribution (EBD)

The ABS module and HCU incorporate a strategy called Electronic Brake Distribution (EBD). The EBD strategy uses the HCU as an electronic proportioning valve to create a balanced braking condition between the front and rear wheels and minimize the chance of rear wheel lockup during hard braking. A slight bump may be felt in the brake pedal when the EBD adjusts the front to rear proportioning during a braking event.

ABS with AdvanceTrac(R) and RSC(R)

The AdvanceTrac(R) with RSC(R) system is made up of the following 3 distinct vehicle systems:

- Traction Control System - helps to avoid excessive drive-wheel spin and loss of traction
- Electronic Stability Control (ESC) - helps to avoid skids and lateral slides
- RSC(R) - helps to avoid vehicle roll-over

Traction Control System

The traction control system aids in the prevention of excessive wheel spin which will allow the vehicle to maintain traction during acceleration. This is accomplished in the same manner as anti-lock braking but also includes the use of the PCM for modulating engine torque.

ESC and RSC(R) Systems

Both systems constantly monitor vehicle direction of travel relative to the driver's intended course and aid in keeping the vehicle traveling along that course. The RSC(R) system also monitors the vehicle roll motion and aids in keeping the vehicle stable during sudden or abrupt maneuvers. This is accomplished in the same manner as anti-lock braking and traction control.

When any of the above 3 systems activate, the driver may notice the same operational symptoms as ABS along with the following additional symptoms:

- A small deceleration or a reduction in the acceleration of the vehicle (PCM modulating engine torque)
- The stability/traction control indicator (also known as the sliding car icon) flashes (indicating a traction or stability event is taking place)

Traction Control Switch

The traction control switch can be used by the driver to disable and enable the traction control systems. When the switch is pressed, traction control is disabled. When the system is disabled the stability/traction control OFF indicator (sliding-car OFF icon) in the Instrument Cluster (IC) (or message center if equipped) will illuminate. The standard anti-lock control system cannot be disabled through the use of the traction control switch.

Trailer Sway Control

Trailer sway control is a unique function in the AdvanceTrac(R) with RSC(R) system that will recognize and aid in reducing trailer sway. The trailer sway control system continually monitors the steering wheel rotation sensor and the yaw rate sensor to identify specific, increasing yaw oscillations that occur during a trailer sway event. If the trailer sway event exceeds certain, programmed parameters, the ABS module and the HCU will modulate brake fluid pressure to specific brake caliper(s) and the PCM will modulate engine torque until the trailer sway is reduced below the programmed parameters.

When the trailer sway control system activates, the vehicle will produce the same noticeable symptoms as it does when the traction control and ESC systems activate. In addition, the message center will display TRAILER SWAY, REDUCE SPEED.

The trailer sway control system will only activate when the vehicle speed exceeds 64 km/h (40 mph). The system can be disabled during any key cycle. Refer to the Owner's Literature for information on disabling the system. The system will be re-enabled when the ignition is cycled from RUN to OFF and back to RUN.

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