Audi A8 2019 Service Training page 80

Function
The radar sensors continuously monitor the traffic follow-
ing behind the vehicle whenever Audi side assist is inactive.
J769 and J770 send signals they receive as data to Airbag
Control Module J234 via FlexRay data bus (channel "B").
The information supplied by ABS/ESC Control Module J104
shares information regarding the vehicle speed. The airbag
control module calculates the speeds of the following
vehicles on the basis of this information.
The following information is therefore available to
Audi pre sense rear :
1)
› Distance of following vehicles.
› Speed of following vehicles.
› Speed of own vehicle.
Audi pre sense rear now initiates the following actions,
which can be subdivided into two phases.
Phase 1
If the driver in the following vehicle reacts during this
phase, for example, brakes or takes evasive action, and
Lane Change Assistance Control Modules J769 and J770 no
longer detect a critical situation, then no further action.
Phase 2
If the critical situation still exists, the side windows and the
panoramic sunroof are closed. If installed, the electrical
head restraints on the seats move upward and the
1)
electrical upper backrests
forward. If the vehicle is equipped with pneumatic seats,
the seat and backrest side bolsters are inflated.
Approximately one second after the side windows, the
panoramic sunroof, the seat adjustment and the side bol-
sters are activated, the instrument cluster indicates that
Audi pre sense is active.
A precondition is that the following vehicles are within the detection range of the radar sensors.
1)
76
(seat adjustment) move
1)
A critical situation is defined as a situation in which a follow-
ing vehicle would collide with the rear end of one's own
vehicle unless further action is taken by the driver of the
following vehicle. Taking the available information as a basis,
the airbag control module decides which actuators to acti-
vate. It relays this information to different control units such
as Sunroof Control Module J245. The other control modules
receive this data and activate the relevant actuators.
Audi pre sense rear
RECAS warning
662_092
662_093