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PSM intervenes and corrects the course if the actual direction of motion deviates from the desired course (steering-wheel position): It brakes individual wheels as needed.
If necessary, PSM also influences the engine power or the gear-changing characteristic of Tiptronic S in order to stabilize the vehicle.
The events below inform the driver of PSM control operations and warn him to adapt his driving style to the road conditions:
Examples of PSM control operations
When PSM is switched off, wheel-specific brake interventions and the anti-slip regulation system (ASR) are also inactive.
The automatic brake differential (ABD) remains on.
Off-road PSM (PSM in the off-road driving program)
When the off-road driving program is active, an off-road PSM specially matched to off-road driving is activated to improve traction.
In order to improve driveability on difficult terrain, the response of the off-road PSM is less sensitive in the low speed range when the vehicle is set to the off-road driving program.
If the brakes are highly stressed, the automatic brake differential (ABD) switches itself off to protect the brakes. It remains deactivated until the brake system has cooled sufficiently again.
Automatic brake differential (ABD)
The ABD system controls the front and rear axles separately. If one wheel of an axle starts to spin, it is braked so that the other wheel on the same axle can be driven.
ABD recognizes different driving states, and it features control strategies adapted to these states. In situations in which little propulsive power is required, such as when the vehicle moves off on a level gravel surface, traction control already becomes active at low engine speeds. If a large amount of propulsive power is required, such as when moving off on an uphill slope or for rapid acceleration, the ABD system is adapted accordingly.
Anti-slip regulation (ASR)
The anti-slip regulation system prevents the wheels from spinning by adjusting the engine power, thereby ensuring good lane-holding ability and stable handling.
Engine drag torque control (MSR)
In conditions of excessive slip, the engine drag torque control system prevents all driven wheels from locking up when the vehicle is overrunning. This is also the case for downshifts on a slippery road.