AUDI A6 2005 C5 / 2.G Electrics System Training Manual
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Vehicl e ke y
The key has a mechanically coded hinged bit for the 
lock cylinder in the driver’s door and the tailgate/
boot lid. The transponder function is integrated into 
the electronics and also works without a battery. 
An integrated battery powers the electronics for the 
radio remote control and Advanced Key functions. 
A new feature here is the bi-directional data 
exchange between the radio-control key and the 
control unit for access and start authorisation via 
the antenna for central locking and anti-theft 
warning system R47. This is used to transfer the 
status of the central locking system into the key. 
If a button outside of the function range of the key 
is pressed, the LED integrated in the key shows the 
lock status of the vehicle. The lock status displayed 
is always the status, which was achieved using this 
key when central locking was last actuated. 
If the vehicle is opened or locked in the interim 
period using a second key, this does not change the 
lock status in the first key.
Furthermore, the radio frequency is changed from 
433 MHz to 868 MHz for the first time in many 
countries. This radio frequency is ideal for data 
communication between vehicle keys and the 
control unit. 
Since this frequency can only be used for very short 
transmission pulses, any interference from 
long-term radio transmitters, such as baby phones, 
wireless headsets, etc. is eliminated.
326_138
326_058 Vehicle within key range
Vehicle outside of key range, 
last vehicle status is locked Signals from the key LED
Vehicle outside of key range, 
last vehicle status is not locked
Approx. 4 seconds on
off
on
off
on
off  
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The control unit is only installed together with the 
Advanced Key option. 
It is located at the right of the dash panel, behind 
the glove compartment.
It evaluates the signals from the outer door handle 
sensors and then activates the antennae for access 
and start authorisation.
The capacity-based operating sensors in the outer 
door handle detect any contact on the handle and 
send a signal shortly afterwards to the antenna 
read-in unit for keyless access authorisation. 
The antenna read-in unit evaluates the signal and 
then sends a query to the vehicle key via the 
antennae for access and start authorisation.
The sensors switch off after approx. 80 hours once 
the vehicle is locked or after 20 actuations without 
an authorised key.
Convenience electrics
326_097
Antenna read-in unit for keyless access authorisation J723
Sensors for outer door handle contact G415 - G418
326_096  
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Four transmitting antennae are distributed in the 
vehicle and are used by the vehicle for radio 
communication with the vehicle key. The antennae 
transmit on a frequency of 24.5 kHz. The vehicle key 
evaluates all four signals and determines the 
position in or on the vehicle based on the field 
strength of the individual antennae. 
The antennae are located:
–in the rear doors
–in the centre console
–in the rear bumper
The start/stop button works in the same way as the 
button module, which was first used in the A8 ‘03. 
For safety reasons, the button positions are 
evaluated both by the control unit for access and 
start authorisation and by the switch for access and 
start authorisation signal. 
Antennae for access and start authorisation E134 - R138
Button for access and start authorisation E408
326_086 326_098  
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Opening the vehicle
Convenience electrics
326_055 Antenna for 
central locking and 
anti-theft warning 
system
R47
Antenna on driver’s 
side for access 
start authorisation
R134Antenna on 
passenger’s side for 
access start 
authorisation 
R135Passeng er 
compartment 
antenna 1 for start 
authorisation 
R138
Boot antenna for 
access 
start authorisation
R137
Switch for 
access and start 
authorisation
E415
Antenna read-in 
unit for keyless access 
authorisation
J723 Control unit for 
access and 
start authorisation
J518
Door control unit, 
driver’s side
J386
Central control unit
for 
convenience system
J393Sensor for 
outer door 
handle contact, 
driver’s side
G415  
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1 The driver puts his/her hand into the finger well 
of the door handle. The sensor for outer door 
handle contact G415 sends the information 
"Finger in finger well" to the antenna read-in unit 
for keyless access authorisation J723.
2 The antenna read-in unit sends an alarm signal 
to the vehicle key via the antenna for access and 
start authorisation R134.
3 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 on the vehicle and sends 
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 information is forwarded by the switch for 
access and start authorisation E415 to the 
control unit for access and start 
authorisation J518, where it is evaluated.6 The control unit for access and start 
authorisation sends the information "Opening 
vehicle" on to the central control unit for the 
convenience system J393 and to the door control 
unit, whose door handle initiated the key query.
7 The door control unit, which received the 
instruction from the control unit for access and 
start authorisation, activates the lock unit, which 
unlocks the door.
8 The central control unit for the convenience 
system J393 sends the information "Opening 
vehicle – Advanced Key" to CAN Convenience.
9 The normal unlocking process takes place. 
This involves disarming, unlocking, 
acknowledgement flashing and switching on of 
the interior light. In addition to 
acknowledgement flashing, the control unit for 
access and start authorisation also sends the 
lock status to the vehicle key via the switch for 
access and start authorisation and the antenna 
for central locking and anti-theft warning 
system R47.  
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Starting the vehicle using the button
Convenience electrics
326_056 Antenna for 
central locking and 
anti-theft warning 
system
R47
Antenna on driver’s 
side for access 
start authorisation
R134Antenna on 
passenger’s side for 
access start 
authorisation 
R135Passenger 
compartment 
antenna 1 for access 
and start 
authorisation
R138
Boot antenna for 
access 
start authorisation
R137
Switch for access 
and start 
authorisation
E415
Antenna read-in 
unit for keyless access 
authorisation
J723 Control unit for access 
and start authorisation
J518
Data bus diagnosis 
for data bus
J533Engine control unit
J623 Button for access 
and start 
authorisation
J408  
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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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Immobiliser 4
Convenience electrics
The immobiliser 4 technology is used in the 
Audi A6 ’05.
This means that all components must be "taught" 
online, as is already the case with the Audi A8 ´03 
and the Audi A3 ´04.
The following components are integrated into the 
immobiliser:
– The control unit for access and 
start authorisation
– The engine control unit
– The vehicle keysControl unit, which is not integrated into the 
immobiliser
Control unit, which is integrated into the 
immobiliser
Master control unit
PC/mainframe
326_099
Immobiliser and component protection
E415 J518
J533 J623  
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New identity
As is already the case with the Audi A8 ‘03 , if a 
control unit is stolen, it is no longer necessary 
(for safety reasons) to also replace the remaining 
control units, which are integrated in the 
immobiliser.
In this case, the "New Identity" function must be 
used for the control unit for access and start 
authorisation and the engine control unit.
It is only a matter of installing a new lock set before 
using the "New Identity" function.
The switch for access and start authorisation E415 
reads in the key code in electronic form only. 
The hinged bit coding is not evaluated signal. 
The ignition switch is not par t of the lock set for this 
reason.
Component protection
As is already the case with the Audi A8 ’03, the 
Convenience and Infotainment control units are also 
integrated within the "Component protection" safety 
system.
As a result, these control units must be adapted to 
the specific vehicle once they have been installed.
The data bus diagnosis interface is integrated into 
the "Component protection" function for the first 
time. Since component protection works via a 
number of control units, the Startup menu in 
"Guided fault-finding" is not assigned to any one 
control unit and can be found directly under the 
self-diagnosis systems.
326_122 326_075
Audi
Audi A6 2005>
2005 (5)
Saloon
BBJ 3.0l Motronic / 160 kW Guided fault-finding
Function test
Teaching driving authorisation 
systems
Te s t i n g   q u e r y
The following options are available:
1. Adapt the driving authorisation system to suit 
the existing immobiliser
2. Assign a new identity to the immobiliser and 
re-teach the components
3. Terminate the function test
326_074
Audi
Audi A6 2005>
2005 (5)
Saloon
BBJ 3.0l Motronic / 160 kW Guided fault-finding
Function/component selection
Selecting a function or component
Body (Rep. Gr. 01; 50 - 97)
Electrical system (Rep. Gr. 01; 27, 90 - 97)
Component protection functions
13 – Distance control, Component protection
05 – Access and start authorisation, Component protection
15 – Airbag, Component protection
06 – Seat adjust. with memory, front pass. side, Comp. protection
36 – Seat adjust. with memory, front driver’s side, Comp. protect.
46 – Central module for convenience system, Comp. protection
66 – Seat adjustment with memory, rear, Component protection
07 – Display/operator unit, front, Component protection
17 – Dash panel insert, Component protection
27 – Display/operating unit, rear, Component protection
Switch for access and start authorisation E415  
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External lights
Front headlights
Three different front headlights are used in the 
Audi A6 ’05:
– Halogen headlights
–Bi-xenon headlights
–Adaptive light
Halogen headlights
Halogen headlights come as standard.
The following lamps are fitted in the halogen on the 
vehicle equipment:
– W5W lamp for parking light
– H1 lamp for high beam headlight and headlight 
flasher
– H7 lamp for dipped beam headlight and dimmed 
as a daytime driving light
– An orange PY21W bulb as the direction indicator 
light
The daytime driving light in the halogen headlight is 
only available for Canada and the Northern 
countries (Scandinavia). It is active when 
terminal 15 is switched on and the parking light or 
dipped beam light is off.
The following country-specific variants exist:
– The daytime driving light is part of the fog lights 
for Canada and 
– 3457NA flasher lamps are used for USA and 
Canada.
A manual headlight range control system – with 
potentiometer – is installed for halogen headlights.
Convenience electrics
326_087
326_149
12 3 4 5
1W5W lamp
2H1 lamp
3H7 lamp
4 PY21W lamp
5D2S lamp