Component Description

WARNING: This page is about a different car, the 2015 Ford C-Max. However, it is still accessible from the selected car via links, so may be relevant.

Anti-Lock Brake System (ABS) Module

The ABS module is attached to the HCU and is the electronic control unit for all of the ABS and stability control systems. The ABS module monitors all sensor inputs and all HS-CAN messages that relate to ABS and stability control, then directly controls the solenoid valves and the hydraulic pump motor in the HCU.

The ABS module can be serviced separately from the HCU. When a new ABS module is installed, it must be programmed with the vehicle configuration information. Refer to: Module Configuration - System Operation and Component Description .

When an ABS or stability control system fault has been corrected or a new component has been installed, the ABS module must be calibrated. The calibration procedures are required for the brake system to operate correctly. stability control sensors to learn the zero-position of the vehicle which means the vehicle must be on a level surface and not moving.

There are 4 calibration routines that must be performed:

Interactive Vehicle Dynamics (IVD) Initialization
Multi-Calibration
Inlet Valve Calibration
Master Cylinder Isolation Calibration

All 4 routines are carried out using a diagnostic scan tool, make sure to follow all diagnostic scan tool directions .

Brake Booster Travel Sensor

The brake booster travel sensor is a linear potentiometer used by the ABS module to monitor brake booster membrane travel distance. The sensor is hardwired to the ABS module by 3 circuits. One circuit is for the 5 volt sensor supply, one circuit is for sensor ground and one circuit is for sensor output. The sensor output ranges from 0.2 volt to 4.7 volts, depending on how far the brake booster membrane travels.

Brake Booster Vacuum Pump

The brake booster vacuum pump is a single speed electric motor pump used to supply vacuum to the brake booster to enhance brake system performance.

Brake Booster Vacuum Sensor

The brake booster vacuum sensor is a piezoelectric device used by the ABS module to monitor the vacuum in the brake booster. The sensor is hardwired to the ABS module by 3 circuits. One circuit is for the 5 volt sensor supply, one circuit is for sensor ground and one circuit is for sensor output. The sensor output ranges from 0.2 volt to 4.9 volts, depending on the amount of vacuum in the booster.

Brake Pedal Travel Sensor

The brake pedal travel sensor (also known as the brake pedal angle sensor) is a Hall-Effect device used by the ABS module to monitor the speed of application and the direction of travel of the brake pedal. The sensor contains 2 opposing sensors that send the information directly to the ABS module. Four circuits connect the brake pedal travel sensor to the ABS module; one circuit is for the 5 volt sensor supply, one circuit is for sensor ground and the other 2 circuits are for sensor output. The sensor supplies a PWM output to the ABS module.

Hydraulic Control Unit (HCU)

The HCU contains the solenoid valves, the hydraulic pump motor and the pressure sensor used by the ABS for the various stability control systems. The HCU can be serviced separately from the ABS module.

There are 4 calibration routines that must be performed:

Interactive Vehicle Dynamics (IVD) Initialization
Multi-Calibration
Inlet Valve Calibration
Master Cylinder Isolation Calibration

All 4 routines are carried out using a diagnostic scan tool, make sure to follow all diagnostic scan tool directions .

Stability Control Sensors

The stability control sensors for the vehicle dynamic system consist of the yaw rate sensor, lateral accelerometer, longitudinal accelerometer and roll rate sensor. The sensors are housed in the RCM which sends sensor information to the ABS module over a private HS-CAN. If any of the sensors are defective, a new RCM must be installed.

The yaw rate sensor measures the yaw angle which is the difference between the direction the vehicle is pointing when cornering and the direction the vehicle is actually moving.
The longitudinal accelerometer measures the acceleration and deceleration of the vehicle as it moves forward and backward.
The lateral accelerometer measures the force created when a vehicle corners that tends to push a vehicle sideways.
The roll rate sensor measures the rate of rotation of the vehicle along the centerline of the vehicle from front to back.

Lateral acceleration has 2 forms. The first is the centrifugal acceleration that is generated when the vehicle travels around in a circle. The second is the acceleration due to gravity. On level ground there is no lateral acceleration due to gravity. However, if the vehicle is parked sideways on a bank or incline, the sensor measures some lateral acceleration due to gravity, even though the vehicle is not moving.

SASM

The SASM transmits steering wheel position, direction and speed of rotation information on the HS-CAN. The module is self-monitoring and capable of setting Diagnostic Trouble Codes (DTCs). The SASM is self calibrating and will learn the vehicle straight-ahead position as it is driven. However, when a new SASM is installed, the module must be programmed with the correct vehicle information. Refer to: Module Configuration - System Operation and Component Description .

Steering Wheel Rotation Sensor

The steering wheel rotation sensor uses 2 optical sensors and a slotted wheel to measure the steering wheel rotation angle, speed and direction of rotation. The sensor is located inside the SASM and is serviced with the module.

Vacuum Pump Relay

The ABS module uses a standard mechanical relay and a solid state relay to activate the vacuum pump.

Wheel Speed Sensor

On vehicles not equipped with active park assist, all 4 wheel speed sensors are active (magneto resistive) sensors that operate on the Hall-effect principle to generate a square wave signal that is proportional to the rotational speed of the wheel. Because these are active sensors, receiving voltage from the ABS module and then sending a varying voltage back to the ABS module, they are able to detect much lower rotational speeds than passive (magnetic inductive) sensors. Each wheel speed sensor is connected to the ABS module by 2 circuits. One circuit provides voltage for sensor operation and the other circuit provides sensor input to the ABS module.

On vehicles equipped with active park assist, both rear wheel speed sensors are active, bi-directional sensors. Each of the 2 sensors contain 2 sensing elements mounted side-by-side. Because the 2 sensing elements are mounted next to each other the 2 voltage signals are slightly out of phase, which causes one element to generate a voltage signal before the other element. This allows the ABS module to not only determine wheel speed, but also wheel direction for active park assist.

Wheel Speed Sensor Encoders

The wheel speed sensor encoders are several magnets arranged in a circle around one side of the wheel bearing in alternating poles. As the wheel bearing rotates the wheel speed sensor is exposed to alternating north-south magnetic fields. The encoder is part of the wheel bearing and is serviced with the wheel bearing.