Audi V8 Service page 47

Crash signal
Signal traces for crash signal using oscilloscope
function of VAS 5051
5 V/Div.
In the event of a crash where the belt
tensioners/airbags are triggered, the engine
control unit deactivates actuation of the fuel
pump relay. This prevents excessive quantities
of fuel escaping if the fuel system is damaged.
The crash signal is a square-wave signal with a
specific signal ratio (high level to low level).
The signal is transmitted continuously by the
airbag control unit.
5 V/Div.
0,1 s/Div.
T
Triggering range
0,5 s/Div.
Automatic mode
In the event of a crash, the signal ratio is
inverted for a defined period of time. During
this period, the signal ratio is inverted relative
to the standard signal so that the supply of
fuel is shut off until the engine is restarted.
In addition, the "crash shut-off" fault is
stored.
The fault entry can only be deleted
using the diagnostic tester.
Recorder mode
Standard signal
Crash triggering
SSP217_058
Crash signal
with triggering
SSP217_059
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