2009 Saab 9-3 Owner's Manual - Page 173

93_US_MY09.book Page 173 Tuesday, April 15, 2008 10:30 AM Starting and driving 173 All-wheel drive (XWD) 3 Essentially, the system consists of a PTU (Power Take off Unit), propeller shaft, RDM (Rear Drive Module which contains an electronically controlled plate clutch, final drive gear and differential) and driveshafts. This system enhances driving characteristics and stability. The system is always active and cannot be deactivated. It works together with the ESP system and the engine and transmission control modules. When driving at a constant speed, approx. 95% of the torque is distributed to the front wheels and approx. 5% to the rear wheels. The torque is distributed steplessly and instantaneously between the front and rear wheels, depending on the driving conditions. If the car is fitted with eLSD (electronically controlled plate clutch between the rear wheels), the torque can also be distributed individually to the relevant rear wheel. For optimum system function, the car's tires should not have varying degrees of wear. When the XWD system requires service, the following message is shown on the SID: Service XWD. When the service message is displayed, the XWD system may have limited functionality (or be completely disabled in some cases, i.e. the car switches to front-wheel drive). Contact a workshop for information. We recommend that you contact an authorised Saab dealer. Traction Control System (TCS) Anti-spin system WARNING When driving normally, the TCS system helps to improve the car's stability, and driveability under slippery road and extreme driving conditions. The TCS must not be regarded as a system to enable the driver to maintain higher speeds. The same precautions must be adopted as normal for safe cornering and driving on slippery roads. 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 speed sensors to determine whether any wheel is spinning. If any wheel is spinning, this is reduced on all-wheel drive cars initially by changing the torque distribution, secondly by reducing the engine torque, and thirdly with the aid of the wheel brakes. On front-wheel drive cars, wheelspin is reduced initially by reducing the engine torque, and secondly with the aid of the wheel brakes.