may also be referred to as ASC+T
(Automatic Stability Traction).
The ASC system improves traction by
electronically applying the rear brakes
when the rear drive wheels are
spinning at a faster rate than the front
wheels. The combined ABS/ASC
control module, operating through the
ABS hydraulic control unit, modulates
braking force at the rear wheels.
In addition, ASC will deactivate
individual fuel injectors and override
the motor driven throttle to reduce
engine torque and maintain vehicle
traction. Because the throttle is
controlled electronically the driver
cannot increase the engine power
output during ASC intervention
regardless of how far the accelerator
pedal is pushed.
The components that comprise the
ASC system also function to replace
the limited slip differential available in
previous models. Even with the ASC
system turned off, if the ASC control
module senses a difference in wheel
speed (one wheel spinning) the control
module will apply modulated braking
force to the slipping wheel until traction
is regained, but will not override fuel
injection function.
Traction control also comes into
operation during deceleration.
Decelerating on snowy or icy road
surfaces can lead to rear wheel slip. If
a rear wheel starts to drag or lock up,
the ASC system can limit the problem
by adjusting throttle, fuel injection and
ignition timing.
A switch on the center console is used
to toggle the ASC on or off.
The ASC system is designed to be
maintenance free. There are no
adjustments that can be made. Repair
and troubleshooting of the ASC system
Suspension, Steering and Brakes — General
http://ebahn.bentleypublishers.com/BMW/3/E46/Repair%20Manuals/3...
5 of 24
2/25/2009 10:24 PM