Mazda Training manual — part 94

Dynamic Driving Safety Systems

TCS

During TCS Control

•

When the wheel spin of the driven wheels exceed a specified limit, engine torque is
reduced via the PCM by cutting the fuel off, changing the ignition timing, closing the
throttle valve (only on vehicles with electronic throttle valve) and/or brake force is applied
to the corresponding wheel in order to prevent it from spinning.

•

The traction control via the brake system can operate in three ways:

–

Pressure increase mode

–

Pressure hold mode

–

Pressure reduction mode

•

To simplify the explanation, the following pages describe TCS control when the right
front wheel, on a front wheel drive vehicle, is spinning.

Curriculum Training

02-35

TCS

Dynamic Driving Safety Systems

Pressure Increase Mode

•

Based on the input signals from the wheel speed sensors, the CM recognizes that the
wheel is spinning. Based on all input signals, programmed parameters and internal
calculations the CM decides whether it is necessary to actuate the brake system and/or
to reduce the engine torque. The following steps explain how the wheel spin is prevented
by activating the brake system.

NOTE: If the CM decides that the engine torque has to be reduced, it sends a corresponding

signal to the PCM. The PCM then reduces the engine torque by cutting the fuel off,
changing the ignition timing and/or by closing the throttle valve (only on vehicles with
electronic throttle valve).

•

The CM actuates the traction switching solenoid valve in the brake circuit for the RF and
LR wheel. This is done to separate the brake circuit from the brake master cylinder and
to enable the pump to build up pressure in the corresponding brake circuit.

•

To make sure the TCS operation for the RF wheel does not affect the LR wheel, the CM
activates the LR inlet solenoid valve.

•

The pump motor is switched on, pressure in the corresponding brake circuit is built up,
and brake force is applied to the spinning wheel.

LF-RR

OFF (open)

RF-LR

ON (closed)

LF

OFF (open)

RF

OFF (open)

LR

ON (closed)

RR

OFF (open)

LF

OFF (closed)

RF

OFF (closed)

LR

OFF (closed)

RR

OFF (closed)

Pump motor

ON (operating)

L2003_T02009

Traction control solenoid valve

Inlet solenoid valve

Outlet solenoid valve

02-36 Curriculum

Training

Dynamic Driving Safety Systems

TCS

L2003_02021

1

Master cylinder

7

Inlet solenoid valve

2

ABS/TCS HU/CM

8

Outlet solenoid valve

3

Damper chamber

9

Brake calliper LR

4

Pump motor

10

Brake calliper RF

5

Pump

11

Traction control solenoid valve RF/LR

6 Reservoir

Curriculum Training

02-37

TCS

Dynamic Driving Safety Systems

Pressure Hold Mode

•

When the CM detects that wheel spin is reduced, it switches to pressure hold mode by
additionally activating (closing) the RF inlet solenoid valve, to maintain the built up
pressure inside the corresponding brake calliper. Furthermore, the CM switches the
pump motor off.

LF-RR

OFF (open)

RF-LR

ON (closed)

LF

OFF (open)

RF

ON (closed)

LR

ON (closed)

RR

OFF (open)

LF

OFF (closed)

RF

OFF (closed)

LR

OFF (closed)

RR

OFF (closed)

Pump motor

OFF (stopped)

L2003_T02010

Traction control solenoid valve

Inlet solenoid valve

Outlet solenoid valve

02-38 Curriculum

Training