2009 Saab 9-5 Owner's Manual - Page 163

95_US_MY09.book Page 163 Tuesday, April 15, 2008 11:03 AM Starting and driving 163 Electronic Stability Program (ESP®) WARNING When driving normally, the ESP® system will help to improve the stability of the car. This does not mean that car can be driven faster. The same care and prudence as normally applied should be displayed on cornering and when driving on slippery roads. The system employs both the antilock braking system (ABS) and the traction control system (TCS). It is a system that helps the driver to stabilize the car in unusual circumstances that would otherwise be more difficult to handle. How the ESP® system works The system can help to prevent the car from skidding by braking one or several wheels independently of the driver. The engine output is then also reduced to prevent the driving wheels from spinning. The car has sensors that measure wheel speed, yaw acceleration, lateral acceleration, steering wheel position and braking pressure. The values provided by these sensors are used to calculate the actual direction of the car. If this direction does not agree with that intended by the driver, calculated from the steering wheel position, the ESP® is engaged. The ESP® system improves the driver's chances of retaining control over the car in critical situations. To ensure that the system works as designed, the dimensions of all four tires must be the same. The illustration shows how the system brakes one or more wheels (and with varying braking force for each wheel) in order to increase the car's chances of following the direction in which the driver wants to drive.