Theory of Electronic Control

Traction Control Systems are referred to as Automatic Stability Control (ASC), Automatic Stability + Traction Control (ASC+T), Dynamic Stability Control (DSC) or All Season Traction (marketing term). The traction control system has gone through several evolutions since its introduction in Model Year 1988. While each new version offered new innovations, the principle of traction control remains the same for any of these versions.

The link between the vehicle and its driving environment is established by the frictional contact between the tires and the road surface. The ability to control the vehicle, while driving, is lost as a result of excessive wheel spin or slip if either rear tire exceeds its ability to:

^ Maintain traction
^ Accept side forces to maintain directional control (lateral locating forces)

The primary function of the traction control system is to maintain traction and stability of the vehicle regardless of the road surface condition. This is achieved by reducing the drive torque applied to the rear wheels or pulsing the rear wheel brakes to eliminate wheel slip depending on the version of traction control installed.

The electronics for traction control operation are incorporated in the ABS control module and share many of the same components and sensors. The module determines the speed of the vehicle through a calculated average of the four wheel speed sensor inputs. Wheel slip/spin is then recognized by comparing the speed of the driven wheels to the front wheels.

A critical slip ratio of up to 5% between the wheels will cause the traction control regulation to begin. This slip ratio is established when the control module detects a wheel speed difference of 2 MPH or higher.