Brief description, TC/ABS 5.3: TCS

WARNING: This page is about a different car, the 2001 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

The TCS function in the TC/ABS control module works by reducing engine torque (addressing a request to the Trionic) and applying the brakes on the driven wheels during TCS modulation.

The rotational speed of the rear wheels is used as a reference for comparing the speed of the drive wheels individually. When either of the drive wheels rotates at a higher speed than the rear wheels, this is described as wheel spin. The magnitude of this wheel spin and the speed of the car are decisive for the manner in which the system works. Forward drive is given priority when wheel spin exceeds a limit value at speeds lower than 22 km/h (13.5 mph) at which point the system will first employ braking and then engine torque limitation.

The transfer of lateral force is given priority when wheel spin exceeds a limit value at speed higher than 22 km/h (13.5 mph) so that steering control is maintained, at which point the system will first employ engine torque limitation and then braking.

A certain degree of wheel spin is always allowed so that the sporty feel and handling of the car will still be retained. This varies with the speed of the car, the friction between tires and road surface, and how "aggressively" the car is being driven (position of throttle pedal).