Mazda Training manual — part 92

Dynamic Driving Safety Systems

EBD

Electronic Brakeforce Distribution

•

All current Mazdas with ABS have EBD (Electronic Brakeforce Distribution) which
eliminates the need for a proportioning valve. The B-Series is the only current Mazda
that still uses a proportioning valve (load sensing type) even though it is also equipped
with EBD.

•

The EBD is a function, which is programmed in the ABS CM and needs only minor
modifications to the system. It allows the split in brake force to be adjusted much more
accurately according to the current driving conditions. The EBD detects the difference in
wheel slip between the front and rear wheels with the aid of the wheel speed sensors. If
wheel slip of the rear wheels compared to the front wheels exceeds a specified limit, it
reduces the brake fluid pressure applied to the rear wheels with the aid of the hydraulic
valves in the ABS HU/CM.

•

Handling response is continuously monitored and a larger proportion of the overall
braking force can be applied to the rear brakes when conditions allow. This results in
shorter brake distances and reduced wear due to less thermal stress on the front brakes.

•

EBD operation stops when ABS operation starts.

•

The graph shows when EBD operation begins, and when the CM changes to ABS
operation mode. Furthermore you will notice that the operation by the CM is always done
in advance, and that there is a difference in time between actuating the valves and the
resulting change in pressure/speed. This is because the electronic control is much faster
than hydraulics, and there is also an additional delay due to the momentum of the
vehicle and wheels.

Curriculum Training

02-27

EBD

Dynamic Driving Safety Systems

L2003_02017

X

Time

5

EBD initial control value

Y1 Speed

6 Pressure

reduction

Y2

Rear solenoid valve control

7

Pressure hold

Y3

Brake fluid pressure

8

Pressure increase

1

Vehicle speed

9

Front brake fluid pressure

2

Rear wheel speed

10

Rear brake fluid pressure

3

Front wheel speed

11

ABS control range

4

ABS initial control value

12

EBD control range

02-28 Curriculum

Training

Dynamic Driving Safety Systems

EBD

Brake System Warning Light

•

The EBD system uses the red brake system warning light to indicate a malfunction. The
brake system warning light also indicates malfunctions concerning brake fluid level or
parking brake operation, but whenever the light illuminates the EBD operation is
disabled.

NOTE: If a malfunction occurs and the EBD is disabled, the red brake system warning light

will illuminate. If this happens the driver should stop immediately and check the
brake fluid level and the brake pressure. If the brake fluid level and the brake
pressure are okay, and the parking brake is released, the vehicle should be driven
slowly, or towed by a professional towing service (refer to apropriate owners
manual), to the workshop. Because, if the EBD system fails, the rear wheels can
lock-up easily due to full brake pressure applied to the rear wheels. If this happens,
the vehicle is difficult to steer and tends to skid during braking.

L2003_02018

1

IC

2

Brake system warning light (red)

Curriculum Training

02-29

EBD

Dynamic Driving Safety Systems

Diagnostics

•

Because the EBD is incorporated in the ABS HU/CM, there is no special procedure
available for diagnosis of the EBD. The system is inspected together with the ABS
HU/CM and the related components.

•

The brake system warning light can be inspected:

–

Visually, after switching the ignition on

–

With the aid of the input/output check mode for the IC

–

Monitoring the corresponding PID (see below)

PID

Definition Unit/Condition

BRAKE_LMP

Brake system warning light

ON/OFF

L2003_T02024

02-30 Curriculum

Training