When Intervention Is Necessary; Drive Torque Reduction - BMW 1999-2005 M3 Service Manual

Suspension, Steering and Brakes — General
11 of 24
http://ebahn.bentleypublishers.com/BMW/3/E46/Repair%20Manuals/3...
Pressure release

When intervention is necessary:

The changeover valve in the
hydraulic unit energizes and closes
inlet valves for the two front wheels
and the rear wheel with traction.
The rear brake circuit intake valve is
energized and opened to rear wheel
without traction.
Return/pressure pump is activated
and draws in brake fluid from the
master cylinder and delivers
pressurized brake fluid to wheel
without traction.
Pressure hold and pressure release
cycles are run by cycling inlet and
outlet valve to rear brake caliper
without traction.

Drive torque reduction

In low traction conditions, the ABS
control module request is sent to the
engine control module (ECM) via the
CAN-bus. The ECM accomplishes torque
reduction by implementing the following
measures:
Reducing throttle opening angle
Retarding ignition
Cutting off individual cylinder fuel
injectors
2/25/2009 10:24 PM