2001 Saab 9-5 Owner's Manual - Page 169

Starting and driving 169 Traction Control System How the system works The traction control system (TCS) is designed to prevent wheelspin. This enables the car to achieve the best possible grip and, hence, maximum tractive effort, together with greater stability. The TCS system uses information from the ABS system's wheel sensors to detect when the front (driving) wheels are rotating faster then the rear wheels. It then monitors whether one driving wheel is rotating faster than the other. If so, the faster wheel is retarded until both wheels are rotating at the same speed. If the two front wheels are rotating at the same speed but are turning faster than the rear wheels, the torque from the engine is reduced to eliminate the difference. The process continues until all the wheels are rotating at the same speed. The advantages of the TCS system become most apparent when the cohesion between the front wheels and the road surface is so low that one or both of the wheels would lose their grip were the car not equipped with the TCS, e.g.: • When the car is pulling away or accelerating with the front wheels on different surfaces (e.g. one slippery and one dry). The TCS then functions like an electronic differential lock. • When the car is pulling away or accelerating on a slippery road, in which case the TCS eliminates wheelspin. The same applies when the car is reversing. • On cornering, if there is a tendency for the inner front wheel to rotate faster than the other wheels. • On overtaking. TCS OFF The TCS OFF indicator on the main instrument panel will come on: • If a fault has been detected and the system has therefore been switched off. • If there is a fault in the ABS system. • If the system has been switched off manually. The indicator light will also come on for 4 seconds when the ignition key is turned to ON, while an internal system check is performed. TCS indicator WARNING In normal driving, the TCS system enhances the safety of the car, but it does not mean that the car can be driven faster. The same care and prudence normally applied should be displayed on cornering and when driving on slippery roads. The indicator light will come on for 4 seconds when the ignition key is turned to ON, while an internal system check is performed. The TCS light in the tachometer comes on when the system is operative, i.e. when the wheels are not rotating at the same speed. The fact that the TCS system is operative indicates that the limit for grip has been exceeded and that the driver must exert greater care.