System Description

FAIL-SAFE FUNCTION
If the control unit detects an abnormality, it shuts the Traction Control System (TCS) off and causes the TCS indicator light to come on. However if the abnormality is detected while the TCS is activated, the control unit first establishes the appropriate wheel spin velocity, then shuts the system down, thus preventing excessive wheel spin.

SELF-DIAGNOSIS FUNCTION
If the control unit detects an abnormality, it records a Diagnostic Trouble Code (DTC) which can be used to diagnose the problem. The DTC is shown at the TCS indicator light when the Service Check connector terminals are connected with the SCS service connector.

STEERING ANGLE DETECTION
Steering angle is detected by the steering angle sensor. The disc with the slits of the regular pattern is provided between the facing parts of the Light Emitting Part (LED), and the light receiving part (photo transistor). As the disc rotates, it passes and shuts off the light from the LED. The light which passed through a slit is converted into the electric current by the photo transistor, and the waveform of this electric current is shaped by the comparator to output the disc rotation as the rectangular signal.

The analysis performance of the system is improved by providing the fixed slit in front of the LED, and thereby identifying the brightness and darkness of the light which is received at the photo transistor clear.

The output signal is the 2-phase output (A-phase and B-phase), and the steering wheel turning angle and the turning direction are calculated by the TCS control unit.

VEHICLE SPEED DETECTION
Wheel rotation speed is detected by the wheel sensors, located at each wheel. The signals are sent to the control unit, which compares each wheel's speed and determines whether traction control is required.








ENGINE OUTPUT CONTROL
When the TCS is activated, the TCS control unit signals the TCS control valve actuator and PCM. The actuator is linked to the TCS control valve which is normally returned to fully open position by the two return springs.

Although the throttle valve is still within the driver's control, the engine output is relaxed by the TCS control valve and PCM to achieve optimum traction.