Mazda Training manual — part 85

Dynamic Driving Safety Systems

Fundamentals

Emergency Brake Assist

•

Although all Mazdas are equipped with powerful and reliable brake systems that provide
excellent braking power even at high speeds, a standard brake system cannot prevent a
driver from reacting incorrectly and applying less force to the brake pedal than required
to achieve the shortest braking distance. Especially when the brake pedal starts vibrating
due to ABS operation, many drivers either instinctively release the brake pedal, or do not
increase the applied force further, which does not allow all the wheels to transmit the
maximum possible brakeforce.

•

The EBA automatically detects emergency braking situations by a combination of the
speed and force with which the driver presses the brake pedal. Once such a situation is
detected, the EBA automatically applies full brake pressure to both brake circuits, until
either the driver fully releases the brake pedal and / or the vehicle comes to a stand still
(depending on the vehicle). Of course the vehicle remains steerable during brake
actuation, because the ABS ensures that no wheel locks up.

•

The EBA is either incorporated into the ABS/DSC HU/CM and operates electronically, or
it operates mechanically and is incorporated into the brake booster.

•

The illustration shows typical differences during emergency braking with and without
EBA.

L2003_01014

X Time

2 Experienced driver without EBA

Y Brake fluid pressure

3 Average driver without EBA

1 Average driver with EBA

Curriculum Training

01-19

Fundamentals

Dynamic Driving Safety Systems

Notes:

01-20 Curriculum

Training

Dynamic Driving Safety Systems

ABS

Antilock Brake System

Parts Location

•

The picture is an example and shows the components of the Antilock Brake System
(ABS) on a Mazda3. The ABS consists of the following components:

–

Control module

–

Hydraulic unit

–

Wheel speed sensor

–

Brake switch

–

Brake system warning light

–

ABS warning light

L2003_02001

1

ABS warning light

6

ABS HU/CM

2

Brake system warning light

7

Front ABS pulse rotor

3

Rear ABS wheel-speed sensor

8

Front ABS wheel-speed sensor

4

Rear ABS pulse rotor

9

PCM

5 Brake

switch

Curriculum Training

02-1

ABS

Dynamic Driving Safety Systems

Hydraulic Unit / Control Module

•

The ABS HU/CM (Hydraulic Unit / Control Module) is located in the engine compartment
and is the core component of the ABS. As the name suggests, it controls the hydraulic
operation of the ABS.

•

It regulates the pressure in the brake lines to prevent the wheels from locking up during
braking. This helps the vehicle remain steerable even during emergency braking.

•

Most Mazda vehicles have a control module that is combined with the hydraulic unit.
Depending on the vehicle it is possible to replace only a HU or a CM. On other vehicles,
whenever there is a malfunction in one of the components, the entire HU/CM needs to
be replaced as a complete unit. The last Mazdas built with a control module separated
from the HU (i.e. the CM module is located elsewhere) were the 323 (BJ) with DSC and
the Premacy (CP) with DSC.

•

The ABS HU/CM is connected to all ABS related components and is programmed with
vehicle-specific parameters. The CM decides whether or not it is necessary to assist the
driver in using the brake system, and accordingly operates the brake system via the HU.

•

The CM is connected to all electrical components of the ABS. It activates the valves and
the pump motor inside the HU, the warning light in the IC (Instrument Cluster), and
monitors the components and wiring for malfunction. It provides the power supply for the
wheel speed sensors (only vehicles with active wheel speed sensors), and receives the
wheel speed signals. Based on those signals it calculates the speed of each wheel
individually and the vehicle speed. The difference calculated between the individual
wheel speed and the vehicle speed indicates the slip of each wheel.

•

The wheel speed sensors and the components inside the HU are hardwired to the CM.
Other components can be either hardwired or connected via CAN.

•

The HU is designed to regulate the pressure in the brake lines according to signals from
the CM. In addition to maintaining the steerability, the regulation of the brake fluid
pressure also helps decrease braking distance, wheel spin during acceleration (vehicles
with TCS), and understeering/oversteering during cornering (vehicles with DSC).

•

The components inside the HU are only operated when ABS operation is required. Then
the CM accordingly actuates the pump motor and the valves.

NOTE: Depending on the model, the ABS HU/CM performs a selftest at a vehicle speed of

approximately 20 km/h after switching the ignition on. An operating pump during this
selftest does not indicate a malfunction.

02-2 Curriculum

Training