Electronic Brake Control Module: Description and Operation

System Description





ABS Control Unit Inputs and Outputs for Connector B (12P)

ABS Control Unit Inputs and Outputs for Connector A (22P)





Part 1 of 2





Part 2 of 2

Features
When the brake pedal is pressed during driving, the wheels can lock before the vehicle comes to a stop. In such an event, the maneuverability of the vehicle is reduced if the front wheels are locked, and the stability of the vehicle is reduced if the rear wheels are locked, creating an extremely unstable condition.
The ABS precisely controls the slip rate of the wheels to ensure maximum grip force from the tires, and it thereby ensures maneuverability and stability of the vehicle.
The ABS calculates the slip rate of the wheels based on the vehicle speed and the wheel speed, then it controls the brake fluid pressure to attain the target slip rate.





Grip Force of Tire and Road Surface

ABS Control Unit
Main Control





The ABS control unit detects the wheel speed based on the wheel sensor signal it received, then it calculates the vehicle speed based on the detected wheel speed. The control unit detects the vehicle speed during deceleration based on the rate of deceleration.
The ABS control unit calculates the slip rate of each wheel, and it transmits the control signal to the modulator unit solenoid valve when the slip rate is high.
The pressure reduction control has three modes: pressure reducing, pressure retaining, and pressure intensifying.

Electronic Brake Distribution (EBD) Control
The electronic brake distribution (EBD) function helps control vehicle braking by adjusting the rear brake force before the ABS operates. Based on wheel sensor signals, the ABS control unit uses the modulator to control the rear brakes individually. When the rear wheel speed is less than the front wheel speed, the ABS control unit retains the current rear brake fluid pressure by closing the inlet valve in the modulator. As the rear wheel speed increases and approaches the front wheel speed, the control unit increases the rear brake fluid pressure by momentarily opening the inlet valve. This whole process is repeated very rapidly.

Self-diagnosis
1. The ABS control unit is equipped with a main CPU and a sub-CPU. Each CPU checks the other for problems.
2. The CPUs check the circuit of the system.
3. Self-diagnosis can be classified into 2 categories:
- Initial diagnosis: Performed right after the engine starts and until the ABS indicator goes off.
- Regular diagnosis: Performed right after the initial diagnosis until the ignition switch is turned OFF.
4. When a problem is detected by self-diagnosis, the system shifts to fail-safe mode.





Self-diagnosis Table

NOTE:
- At the DTCs with "*" mark, there are cases that the ABS control unit shifts to fail-safe mode A1, L1 when the ABS control unit detects more than one DTC and for different wheel.
- If the ABS control unit detects the DTCs which have different fail-safe mode individually, the control unit take priority the large number mode.





Operation Mode Table

On-board Diagnosis Function
The ABS can be diagnosed with the Honda PGM Tester.
The ALB Checker cannot be used with this system. For air bleeding, and checking wheel sensor signals, use the Honda PGM Tester. See the Honda PGM Tester user's manuals for specific operating instructions.