Toyota Tundra 2005 Service - Repair - Maintenance page 3873

VSC (Access/Standard Cab)
System Outline
1. ABS Operation
If the brake pedal is depressed suddenly, the ABS controls the hydraulic pressure of the wheel cylinders for all the four
wheels to automatically avoid wheel locking and ensure the directional and steering stability of the vehicle. If the brake pedal
is depressed suddenly, the skid control ECU controls the solenoids in the actuators using the signals from the sensors to
move the brake fluid to the reservoir in order to release the braking pressure applied to the wheel cylinder. If the skid control
ECU detects that the fluid pressure in the wheel cylinder is insufficient, the ECU controls the solenoids in the actuators to
increase the braking pressure.
2. Traction Control Operation
The traction control system controls the engine torque, the hydraulic pressure of the driving wheel cylinders, slipping of the
wheels which may occur at start or acceleration of the vehicle, to ensure an optimal driving power and vehicle stability
corresponding to the road conditions.
3. VSC Operation
Unexpected road conditions, vehicle speed, emergency situation, and any other external factors may cause large under- or
over-steering of the vehicle. If this occurs, the VSC system automatically controls the engine power and wheel brakes to
reduce the under- or over-steering.
To reduce large over-steering :
If the VSC system determines that the over-steering is large, it activates the brakes for the outer turning wheels depending
on the degree of the over-steering to produce the moment toward the outside of the vehicle and reduce the over-steering.
To reduce large under-steering :
If the VSC system determines that the under-steering is large, it controls the engine power and activates the rear wheel
brakes to reduce the under-steering.
Traction control SW
The traction control SW is used to stop the TRAC function. After the engine is started, the TRAC system is stopped (turned
off) and the VSC OFF indicator light lights up. When the traction control SW is pressed again, the TRAC system enters the
stand-by mode. If the engine is stopped and restarted, the TRAC system enters the stand-by mode regardless of the
traction control SW.
4. Mutual System Control
To efficiently operate the VSC system at its optimal level, the VSC system and other control systems are mutually controlled
while the VSC system is being operated.
Engine throttle control
The engine power does not interfere with the VSC brake control by controlling the opening of the throttle and reducing the
engine output.
Engine control and electronically controlled transmission control
The strong braking force does not interfere with the braking force control of the VSC system by turning off the accel. and
reducing changes in the driving torque at shift-down.
VSC system operation indication
The Slip indicator light flashes and the buzzer sounds intermittently to warn the driver that the current road is slippery, while
the VSC system is being operated.
5. Fail Safe Function
If an error occurs in the skid control ECU with actuator, sensor signals, and/or actuators, the skid control ECU with actuator
inhibits the brake actuator control and inputs the error signal to the engine control module. According to the error signal, the
brake actuator turns off the solenoid and the engine control module rejects any electronically controlled throttle open request
from the VSC system. As a result, the vehicle functions regardless of the ABS, TRAC, and VSC systems.
Service Hints
S29 (A), S30 (B) Skid Control ECU with Actuator
(A)46-Ground : Approx. 12 volts with ignition SW at ON position
(A)1, (A) 32, (B) 4-Ground : Always continuity
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2005 TOYOTA TUNDRA (EWD611U)