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