Mazda Training manual — part 86

Dynamic Driving Safety Systems

ABS

•

The HU consists of the hydraulic pump and of 6…12 solenoid controlled hydraulic
valves. One inlet and one outlet valve for each wheel (for B-Series only one inlet and
one outlet valve for the rear axle), two traction control valves for vehicles with TCS and
two additional stability control valves for vehicles with DSC. The HU cannot be
disassembled.

•

Most HUs feature a flow control valve downstream of each inlet valve. The flow control
valve has been integrated to reduce the brake fluid flow noise by narrowing a passage,
and is actuated hydraulically in case of a high-pressure difference upstream and
downstream of the inlet valve.

NOTE: Always keep in mind, that the Dynamic Driving Safety Systems cannot override the

law’s of physics.

L2003_02002

1

Control module

4

ABS pump motor

2

Hydraulic unit

5

Lock lever for connector

3

Brake pipe

6

ABS connector / wiring loom

Curriculum Training

02-3

ABS

Dynamic Driving Safety Systems

Wiring Diagram

L2003_02003

Mazda3

1

ABS fuse 1

11

Battery

2

ABS fuse 2

12

ABS pump motor

3

ABS fuse ignition ON

13

CAN H

4

Solenoid valves

14

CAN L

5

Brake system warning light

15

ABS wheel-speed sensor LR

6

ABS warning light

16

ABS wheel-speed sensor RR

7

CAN driver

17

ABS wheel-speed sensor LF

8

IC

18

ABS wheel-speed sensor RF

9 PCM

19 ABS

HU/CM

10 DLC-2

02-4 Curriculum

Training

Dynamic Driving Safety Systems

ABS

Layout

•

Current Mazda models use ABS with 4 wheel speed sensors and a three or four
channel layout:

–

A three channel layout provides ABS control for each front wheel individually and for
the rear wheels in common according to the “select low” principle. The B-Series is
the only Mazda vehicle still featuring this layout. “Select low” principle means an
ABS control strategy adjusting brake pressure for both rear wheels determined by
the wheel that tends to lock first. Because, the largest influence on a vehicle’s
driving stability is the ability of the rear axle to continue to travel in the desired
direction.

–

A four channel layout allows individual brake pressure control for each wheel. This is
required when either the brake system has a diagonal split layout, as all Mazda
models with front wheel drive have, or when a rear wheel driven vehicle has TCS.
During ABS operation the rear axle is also controlled corresponding to the “select
low” principle. A four channel layout is mandatory for DSC.

Hydraulic Circuit

•

The hydraulic circuit that is explained on the following pages, is a four channel ABS. A
three channel ABS operates similar, except for the fact, that it features only 6 solenoid
valves.

•

The HU for a 4 channel ABS is equipped with 8 solenoid valves that can be activated for
the ABS operation. Four of those valves are the inlet valves, they are used to separate
each single brake calliper from the brake master cylinder and avoid further pressure
increase if the corresponding wheel is about to lock-up. These valves are always open
when not actuated. The other four valves are the outlet valves. They are necessary to
be able to release pressure from each single brake calliper to reduce the applied brake
force on each wheel individually, if a wheel is still about to lock-up after the inlet valve
has been closed. These valves are always closed when not actuated.

Curriculum Training

02-5

ABS

Dynamic Driving Safety Systems

Hydraulic Diagram

L2003_02004

Mazda3

1

Master cylinder

7

Inlet solenoid valve

2

ABS HU/CM

8

Outlet solenoid valve

3

Damper chamber

9

Brake calliper LF

4

Pump motor

10

Brake calliper RR

5

Pump

11

Brake calliper LR

6

Reservoir

12

Brake calliper RF

Operation

•

For easier understanding, only the operation of the left front brake circuit is explained.
The other circuits act similarly.

02-6 Curriculum

Training