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