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Engine Management
Self-diagnosis
The crash signal is checked with respect to
the plausibility of the crash signal and
voltage.
Effect of fault
If the “crash shut-off“ fault is stored in the
engine control unit and is not erased, the fuel
pump is not primed with fuel when the
ignition is switched on (no precompression is
generated in the fuel system). This may result
in delayed starting of the engine.
Further information concerning the
fuel shut-off system can be found
under Vehicle Safety in SSP 207 and
SSP 213.
The fuel shut-off system will not be
incorporated in the Audi A6 and A8
until model year 2000.
Self-diagnosis
The air conditioner requirement interface is
not monitored by the self-diagnosis system.
Effect of fault
The idling speed is not increased which
results in a reduction in the output of cool air
when the engine is idling.
The air conditioner requirement interface
In the case of a high air conditioner output
requirement, the idling speed of the engine is
increased to increase the output of cool air
from the air conditioner compressor.
In some cases, air conditioning requirements
may be such that the “air conditioner require-
ment“ interface is also switched to “high“ at
the air conditioner operating and display unit
whereupon the engine control unit is infor-
med of the increased output requirement.
This can be tested using the “Read measured
value block“ function of the diagnosis tester
(see repair manual).
It is important to note that the function for
increasing the idling speed is not available for
all engine variants, even if the signal is sent
to the engine control unit.
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