Saab 2001 9-3 - Manual (Page 172)

172 Starting and driving
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 accelerat-
ing with the front wheels on different sur-
faces (e.g. one slippery and one dry). The
TCS then functions like an electronic dif-
ferential lock.
• When the car is pulling away or accelerat-
ing 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 instru-
ment 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 man-
ually.
The indicator light will also come on for
4 seconds when the ignition key is turned to
ON, while an internal system check is per-
formed.
TCS indicator
The indicator light will come on for
4 seconds when the ignition key is turned to
ON, while
an internal system check is per-
formed.
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.
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.