Anti-Lock Control

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ANTI-LOCK CONTROL - HYBRID

See the Tribute Hybrid Wiring Diagram for schematic information.

Principles of Operation

Anti-Lock Brake System (ABS)

The ABS control module controls the foundation brake function as well as anti-lock braking.
When the ignition switch is placed in the RUN position, the module carries out a preliminary electrical check. At approximately 20 km/h (12 mph), the hydraulic pump motor is turned on for approximately 0.5 second. Any malfunction of the ABS disables the ABS and the anti-lock brake warning indicator illuminates. However, the power-assist braking system still functions normally.
The ABS control module receives wheel speed readings from each wheel speed sensor and processes this information to determine if an ABS event is necessary. The wheel speed sensor electrically senses each tooth of the wheel speed sensor indicators as they pass through the wheel speed sensor magnetic field.
The active wheel speed sensor generates a signal that is sent to the ABS control module. The wheel speed sensor circuitry connects to the ABS control module through 2 wires and a connector at each wheel speed sensor. When the ignition is turned to the RUN position, the ABS control module carries out a self-test by sending a reference voltage to all of the wheel speed sensors through their circuitry to determine if they are functional.
The ABS control module continuously monitors and compares the rotational speed of each wheel and when it detects an impending wheel lock, modulates brake pressure to the appropriate brake caliper. This is accomplished by triggering the hydraulic control unit (HCU) to open and close the appropriate solenoid valves. Once the affected wheel returns to normal speed, the ABS control module returns the solenoid valves to their normal positions, and normal (base) braking resumes.
The HCU has additional internal solenoid valves incorporated to enable control modulation of the wheel brake pressures.
The ABS control module is self-monitoring. During all phases of operation the ABS control module, with the vehicle in motion, checks for correct operation of the wheel speed sensors. Any malfunction of the ABS will cause the ABS to shut off. Normal power assisted braking, however, remains.

ABS Control Module Configuration

When a new ABS control module is installed, it must be configured. See - Testing and Inspection.

Electronic Brake Distribution (EBD)

The HCU is used as an electronic proportioning valve for electronic brake distribution (EBD). The HCU controls the brake fluid pressure to the rear brakes to help prevent them from applying before the front brakes. If the ABS is disabled due to DTCs being present in the module, the EBD will continue to function unless there is a complete failure of the HCU. When EBD is disabled, the ABS warning indicator also illuminates.

Sensor Cluster (Accelerometer)

The sensor cluster (also called the accelerometer) consists of several different sensors all packaged together in one unit. Four wheel drive (4WD) hybrid vehicles only use the longitudinal accelerometer portion of the sensor cluster. Front wheel drive (FWD) hybrid vehicles do not require the sensor cluster. The longitudinal accelerometer measures the acceleration corresponding to the force involved when the vehicle moves forward and rearward in the horizontal plane, along the centerline of the vehicle's front and rear wheels. This information is used by the ABS control module to enhance the 4WD ABS.