Audi q7 2017, Manual, Page: 21 / 70

17
System characteristics of the reversible safety belt tensioners
• After reducing safety belt slack, the seat belt is released
again.
• If a safety belt is not worn, slack is not reduced for this
safety belt.
• If the front passenger airbag is "off", slack is not reduced
on the front passenger side.
Longitudinal dynamics function
• Reversible safety belt tensioners (J854/J855) communi-
cate with Airbag Control Module J234 via a sub-bus
system. J234 instructs the belt tensioners to reduce the
belt slack.
• In the case of Audi pre sense basic, tensioning of the
reversible safety belt tensioners can take place at speeds
higher than18.6 mph (30.0 km/h) when the longitudinal
and transverse dynamics functions are active. To activate
longitudinal dynamics, the vehicle must be moving
forwards.
An exception here is the crash function in the low relative
speed range (refer to page 18).
Hazard braking
If the brake pressure reaches a defined value during a
hazard braking maneuver, Audi pre sense basic initiates
electrical
partial tensioning of the reversible safety belt
tensioners. A message indicating that Audi pre sense is
active appears in the instrument cluster. No audible signal
is given.
Emergency braking
During an emergency braking maneuver, the safety belt
tensioners are either
partially or fully tensioned .
Depending on the situation, ABS Control Module J104
can instruct the emergency warning flashers to be acti-
vated. A distinction is made between the following two
criteria for emergency braking.
• An emergency braking situation exists if ABS Control
Module J104 detects that brake pressure had reached a
specific value within a defined period of time. If the
conditions are met, Audi pre sense basic initiates electri-
cal
full tensioning of the reversible safety belt tension-
ers. A message indicating that Audi pre sense is active
appears in the instrument cluster. No audible signal is
given.
System characteristics
• If Electronic Stability Control (ESC) is set to
"lift / offroad" of "off" using ASR/ESP Button E256,
the safety belts are
not partially tensioned .
• If Audi drive select is set to "dynamic" or "lift / offroad",
the safety belts are
not partially tensioned .
• If Audi pre sense is switched off in the MMI, the safety
belts are
not partially tensioned either.
• An emergency braking situation exists if the given condi-
tions are not met, but if ABS Control Module J104 has
detected an emergency braking maneuver based on the
pedal rates. If the conditions are met, Audi pre sense
basic initiates electrical
partial tensioning of the revers-
ible safety belt tensioners. A message indicating that
Audi pre sense is active appears in the instrument
cluster. No audible signal is given.
637_019
Driving Profile Selection
Switch Module
E592 ASR/ESP Button
E256
637_041
Audi pre sense
Control Unit 1 for Driving and
Convenience Functions
E791