Toyota Tundra. Manual — part 910

c. BA (Brake Assist)

The primary purpose of the brake assist system is to provide auxiliary brake force to assist drivers
who cannot generate a brake force large enough during emergency braking, thus helping to
maximize the vehicle's braking performance.

Fig. 7: Identifying Brake Assist - System Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

1. Operation description

The skid control ECU receives speed signals from each speed sensor and the fluid pressure
signal from the master cylinder pressure sensor to determine whether brake assist is
necessary. If brake assist is deemed necessary, the skid control ECU sends control signals to
the pump motor and solenoid. The pump and the solenoid valve then control the pressure
applied to each wheel cylinder. The ABS warning light comes on to indicate malfunctions in
the BA system.

d. Changing of TRAC, AUTO LSD and VSC operation permission/disablement through VSC OFF

switch

1. Changing modes

Through the VSC OFF switch, the vehicle can be changed to normal mode, TRAC OFF
mode, AUTO LSD mode and VSC OFF mode.

2009 Toyota Tundra

2009 BRAKES Brake Control - Tundra

Fig. 8: Identifying VSC Off Switch
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Fig. 9: Identifying VSC Operation Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

2WD vehicles and 4WD vehicles in 2H mode

CONTROL MODE INDICATOR LIGHT TABLE

Control Mode

Indicator Light

Slip Indicator Light

AUTO LSD

Indicator Light

VSC OFF Indicator

Light

Normal mode

-

-

-

TRAC OFF mode

o

o

-

2009 Toyota Tundra

2009 BRAKES Brake Control - Tundra

Fig. 10: Identifying VSC Switch Communication Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

4WD vehicles in 4H and 4L mode

CONTROL MODE INDICATOR LIGHT TABLE

2. Drive mode and each function

DRIVE MODE AND FUNCTION TABLE

AUTO LSD mode

o

o

o

VSC OFF mode

o

-

o

HINT:



o: Illuminated



-: Not illuminated

Control Mode

Indicator Light

Slip Indicator Light

VSC OFF Indicator Light

Normal mode

-

o

VSC OFF mode

o

o

HINT:



o: Illuminated



-: Not illuminated

Drive
Mode

VSC OFF

Switch

Brake Control

ABS

EBD

BA

TRAC

A-TRAC

AUTO

LSD

VSC

2WD

Normal

mode

o

o

o

o

-

-

o

TRAC

o

o

o

-

-

o

o

2009 Toyota Tundra

2009 BRAKES Brake Control - Tundra

e. TRAC (Traction Control) (for 2WD vehicles or 4WD vehicles in 2H mode)

The TRAC system helps prevent the drive wheels from slipping if the driver presses down on the
accelerator pedal excessively when starting off or accelerating on a slippery surface.

vehicles

and 4WD

vehicles in

2H mode

OFF

mode

AUTO

LSD

mode

o

o

o

-

-

o

-

VSC OFF

mode

o

o

o

-

-

-

-

4WD

vehicles in
4H and 4L

mode

Normal

mode

o

o

o

-

o

-

-

VSC OFF

mode

o

o

o

-

-

-

-

HINT:



o: Operates



-: Does not operate

2009 Toyota Tundra

2009 BRAKES Brake Control - Tundra