Traction Control Module: Description and Operation

ACCELERATION CONTROL
When the drive wheel speed exceeds the vehicle speed by a given amount, the Traction Control System (TCS) control unit judges that the drive wheels are slipping, and it outputs the traction control signal to reduce engine power.

DECELERATION CONTROL
When the drive wheel speed drops below the vehicle speed by a given amount, the TCS control unit judges that the drive wheels are slipping, and it outputs the traction control signal to control engine braking properly.

HANDLING CONTROL
Based on signals about driving wheel and driven wheel rotational speeds, the control unit calculates the car's "yaw" rate (the turn rate of the car's body). Based on signals from the steering angle sensor, the control unit also calculates the yaw rate expected by the driver. If the difference between actual and expected yaw rates is substantial -- that is, if the direction of the car's body will exceed the driver's expected line the control unit signals the throttle actuator, which closes the throttle valve, thus reducing engine power and maintaining the expected line.

ROUGH ROAD CONTROL
Based on signals from the wheel sensors, the control unit detects a rough road based on frequency of wheel rotational vibration. The control unit then signals the throttle actuator to relax engine power, thus improving acceleration efficiency.

GRIP CONTROL
Based on signals about wheel speed and lateral acceleration, the control unit determines the efficiency of the grip of the tires on the road and signals the throttle actuator to relax engine power if necessary, thus improving grip.





FAIL-SAFE FUNCTION
If the control unit detects an abnormality, it shuts the traction control system 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 service connector.








STEERING ANGLE DETECTION
Steering angle is detected by the steering angle sensor, located on the steering column. The sensor uses two Magneto-Resistor (MR) elements to determine steering angle and direction of rotation. When the driver turns the steering wheel, a magnet in the steering shaft generates waves in the "MR" elements. These waves are amplified and converted into signals which the control unit can interpret as angle and direction of turn.