Electronic Brake Control Module: Description and Operation

HECU (HYDRAULIC & ELECTRICAL CONTROL UNIT)





The ABS control unit performs the following functions:
^ Controls the ABS
^ Calculates vehicle speed
^ Self-diagnostics: Stores malfunction codes, performs ABS control unit self-diagnostic and fail-safe functions with two separated microprocessors.
The ABS control unit continuously checks locking of each wheel and controls each valve to adjust brake fluid pressure if required. The ABS control unit also checks that components are working properly and stops ABS if a malfunction is detected. Then, it is operated as a standard brake system.

SPEED SENSOR
STRUCTURE








The speed sensor detects wheel rotation and consists of a permanent magnet and pickup coil. Sensors for the front wheels are attached to drive shaft and rear hub spindle for the rear wheel.

OPERATION





Since teeth of sensor rotor change magnetic field of sensor, it generates alternative voltage. This voltage is proportional to rotating speed and its period can be changed. It can sense speed of wheel by detecting period.

WARNING LAMP





1. ABS warning lamp
1) It is turned on for three seconds at time of ON of ignition Key and turns off afterwards.
2) It is extinguished at start of operation.
3) It is lighted if system abnormality arise.
4) It is lighted during self-diagnosis.
5) During its lighting, ABS control is interrupted and only ordinary brake operates in same way as ABS, TCS non-installed vehicle.
6) It is lighted when ECU connector is removed.

2. Electronic Brake-force Distribution (EBD) warning lamp
1) It is lighted at time of ON of ignition Key.
2) It is extinguished at start of operation.
3) It is lighted when parking brake switch is ON.
4) It is lighted when brake oil is deficient.
5) It is lighted when EBD control is infeasible.
^ When there is trouble at solenoid valve.
^ When there is trouble in more than one sensor.
^ When there is trouble in ECU.
^ In case of high voltage.

HYDRAULIC CONTROL UNIT (HCU)
The HCU consists of a motor pump assembly in which motor sensor is built, and valve block for controlling ABS pressure.
Motor sensor is built in motor, and output signal, which detects condition of a motor pump assembly, is sent to HECU (for ABS).
Reference
Diameter of front brake pipe holepitch: 0.189 inch (4.8 mm)
Diameter of rear brake pipe holepitch: 0.189 inch (4.8 mm)





The motor pump is a reciprocal 2-line pump and transmits enough pressure to the wheel system, and the valve block controls fluid pressure to each wheel cylinder.