Audi A6 2005 - Electrics Service Training page 27

1 The driver presses the button for access and
start authorisation E408 down fully. The button
sends the information about "Ignition on" and
"Engine start" both to the switch for access and
start authorisation E415 and to the control unit
for access and start authorisation J518.
2 The switch for access and start authorisation
passes the information from the button on to the
control unit for access and start authorisation via
the data lead. The two button information
messages are compared there.
3 The control unit J518 sends a key query to the
antenna read-in unit for keyless access
authorisation J723.
The antenna read-in unit sends a signal to the
vehicle key via all the antennae for access and
start authorisation.
4 Based on the signals, the vehicle key determines
the position in the vehicle and sends its
information to the antenna for central locking
and anti-theft warning system R47.
5 The antenna for central locking and anti-theft
warning system receives the information.
The switch for access and start authorisation
E415 passes the information on to the control
unit for access and start authorisation, which
then evaluates it.
6 Based on the key evaluation, the S contact is
sent to CAN Convenience and the steering is
unlocked.
7 As soon as the steering is fully unlocked,
terminal 15 is switched on.
8 Once terminal 15 has been switched on, data is
exchanged between the engine control unit and
the control unit for access and start
authorisation via the CAN bus. The immobiliser is
then deactivated.
9 The control unit for access and start
authorisation sends the "Start request" signal to
the engine control unit. The engine control unit
checks whether the clutch is depressed or
whether P or N is selected in the case of an
automatic gearbox and then performs the fully
automatic engine start.
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