AUDI A6 2005 C5 / 2.G Electrics System Training Manual
Page 11 of 92
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Audi A6 2005>
2005 (5)
Saloon
BBJ 3.0l Motronic / 160 kW Guided fault-finding
Function/component selection
Selecting a function or component
Electrical system (Rep. Gr. 01; 90 - 97)
01 – Self-diagnosis systems
61 – Battery control
J644 – Control unit for power management, Functions
A – Battery, Charge level
A – Battery, Battery testing
J644 – Power management, General description
J644 – Control unit for power management, Coding
J644 – Read out history data
J644 – Power management, Read measured-value blocks
J644 – Power management, Query fault memory
J644 – Data link tests for generator voltage
J644 – Replace control unit
J644 – Power management, Activate/deactivate Transport mode
Battery change history
Data for the last three battery changes is stored.
Power balance history – driving (= engine on)
The power balance and duration of the last five 
journeys are logged.
Power balance history – idle (= engine off)
The power balance and duration of the last five idle 
times are logged.
Other data is not relevant for Customer Service.
History dataThe diagnosis tester can be used to read out 
data from the control unit for power management, 
which makes it much easier to analyse the on-board 
power supply and the battery. 
Open-circuit voltage history
If the battery open-circuit voltage is less than the 
threshold values of 12.5 volts, 12.2 volts and 
11.5 volts, an entry is written to the history data. 
The last four entries can always be read out.
Voltage measurement starts when 
– CAN Convenience is in Sleep mode and 
– terminal 15 is switched off for at least 2 hours 
and 
– the vehicle’s power consumption is < 100 mA.
Voltage measurement ends when 
– the voltage increases or
– the current increases or
– the control unit triggers Sleep mode or
– the control unit detects a new battery.
Closed-circuit current history
If the closed-circuit current exceeds the threshold 
value of 50 mA, an entry is written to the history 
data. The last ten entries can be read out.
Current measurement starts when 
– CAN Convenience is in Sleep mode and 
– terminal 15 is switched off for at least 2 hours 
and 
– the vehicle’s power consumption is > 50 mA.
Current measurement ends when 
– the current decreases or
– the control unit triggers Sleep mode.
Breakdown analysis
If the control unit for power management detects 
the status "Cannot start vehicle", an entry is written 
to the history data.
Cut-off level history
Data for the last 15 cut-off levels is stored.
Steady battery dischargeThe battery condition is 100 % when the battery is 
charged.
As soon as cut-off level 1 is activated, the MMI 
"Battery condition" display drops to 90 % and then 
goes down to 60 % in steps. If cut-off level 1, 2 or 5 
is set when the display reads 90 %, the message 
"Power-saving mode active" app ears fo r a sho r t time 
on the central display of dash panel insert J285. 
In addition, the battery symbol in the dash panel 
insert indicates power-saving mode for the entire 
load switch-off duration. 
As soon as cut-off level 3 is activated, the "Battery 
condition" display drops to 50 % and then goes 
down to 20 % in steps. 
If the battery condition drops to 10 %, cut-off level 6 
is active. In cut-off level 6, the message 
"B AT TERY LOW" appears in the central di splay of the 
dash panel insert after the ignition is switched on.
326_061 326_061
326_036
POWER-SAVING
MODE
ACTIVE
BATTERY
LOW
Battery condition
Cut-off levels 1, 2 or 5
Cut-off level 3
POWER-SAVING
MODE
ACTIVEBATTERY
LOW
Time/MinutesCut-off level 6
Time/MinutesPOWER-SAVING
MODE
ACTIVE
12 326_123  
Page 12 of 92
Downloaded from www.Manualslib.com manuals search engine Convenience electricsFunction diagramLegend
E369 Central locking button for outer door handle, 
driver’s side*
E370 Central locking button for outer door handle, 
passenger’s side*
E371 Central locking button for outer door handle, 
rear left*
E372 Central locking button for outer door handle, 
rear right*
E408 Button for access and start authorisation
E415 Switch for access and start authorisation
F272 Outer door handle switch, driver’s door*
F273 Outer door handle switch, passenger’s door*
F274 Outer door handle switch, rear left*
F275 Outer door handle switch, rear right*
F305 Switch for gearbox position P**
G415 Sensor for outer door handle contact, 
driver’s side*
G416 Sensor for outer door handle contact, 
passenger’s side*
G417 Sensor for outer door handle contact, 
rear left*
G418 Sensor for outer door handle contact, 
rear right*
J53 Starter relay
J329 Voltage supply relay, terminal 15
J386 Door control unit, driver's side
J387 Door control unit, passenger's side
J388 Door control unit, rear left
J389 Door control unit, rear right
J518 Control unit for access and 
start authorisation
J623 Engine control unit
J694 Voltage supply relay, terminal 75x
J695 Starter relay 2
J723 Antenna read-in unit for keyless access 
authorisation*
R47 Antenna for central locking and 
anti-theft warning system
R134 Antenna on driver’s side for access 
access and start authorisation*
R135 Antenna on passenger’s side for access 
access and start authorisation*
R137 Luggage compartment antenna for access 
access and start authorisation*
R138 Passenger compartment antenna 1 for 
access and start authorisation*
* only for vehicles with Advanced Key
** only for vehicles with automatic transmission
  1 Terminal 50 (to starter B)
  2 CAN Convenience High
  3 CAN Convenience Low
  4 P/N signal from control unit for 
automatic transmission J217**
  5 Terminal 58s (lighting)*
  6 Signal from brake light switch F*
Positive supply
Input signal
Output signal
Ground
Bi-directional line
13
Access and start authorisation
Start request
Ulock  
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326_038  
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The Advanced Key system was introduced with the 
Audi A8 '03 and has been fundamentally revised for 
the Audi A6 ’05. 
The most important new feature is that the control 
unit for access and start authorisation has been 
combined with the actuator for steering column 
locking.
Convenience electrics
System overview  
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326_147
1 Door control unit, driver's side J386
2 Control unit for on-board power supply J519
3 Control unit for access and start 
authorisation J518
4 Switch for access and start authorisation E415
5 Central locking button for outer door handle, 
driver's side E369 
Outer door handle switch in driver’s door F272 
Sensor for outer door handle contact, 
driver’s side G415
6 Antenna read-in unit for keyless access 
authorisation J723
7 Antenna on driver’s side for access 
and start authorisation R134
8 Door control unit, rear left J388
9 Passenger compartment antenna 1 for 
and start authorisation R138
10 Door control unit, passenger's side J38711 Central locking button for outer door handle, 
rear left E371 
Outer door handle switch, rear left F274 
Sensor for outer door handle contact, 
rear left G417
12 Central locking button for outer door handle, 
passenger’s side E370 
Outer door handle switch in passenger’s 
door F273 
Sensor for outer door handle contact, 
passenger's side G416
13 Antenna on passenger’s side for access 
and start authorisation R135
14 Door control unit, rear right J389
15 Antenna for central locking and 
anti-theft warning system R47
16 Central locking button for outer door handle, 
rear right E372 
Outer door handle switch, rear right F275 
Sensor for outer door handle contact, rear 
right G418
17 Boot antenna for access 
and start authorisation R137  
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Division of functions
System control is broken down into three basic 
modules:
– the control unit for access and 
start authorisation J518,
– the antenna read-in unit for keyless access 
authorisation J723 and
– the switch for access and 
start authorisation E415.
All three components communicate with each other 
over a local single-wire bus. 
The control unit for access and start authorisation is 
the master of the system and a participant on 
Convenience. The same control unit is installed for 
all system versions. 
The antenna read-in unit for keyless access 
authorisation is only installed with the 
Advanced Key option. It serves as the interface 
between the antennae, sensors and the control unit 
for access and start authorisation. 
The switch for access and start authorisation is 
installed in various versions, depending on the 
transmission, radio frequency of the central locking 
system and the Advanced Key option. An evaluation 
electronic device is also integrated into the switch.
Convenience electrics
326_064
Access and 
start authorisation 
J518Antenna read-in 
unit for 
keyless access 
authorisation
J723
Switch for 
access and start 
authorisation 
E415  
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Ve rs i on s
The switch for access and start authorisation is 
available in the following versions:
– with and without Advanced Key function
– with and without ignition key anti-removal lock
– for radio frequencies of 315 MHz, 433 MHz or 
868 MHz
Functions
The switch for access and start authorisation 
includes other functions apart from the ignition 
switch function:
– Evaluation of the key position of the ignition 
switch:
The ignition switch evaluates the ignition key 
position using four switches. 
The switch information is transferred to the 
control unit for access and start authorisation in 
binary code via the local bus and also for 
monitoring purposes, via two lines. 
The lock barrel in the ignition switch is not coded 
mechanically, which means that the turning 
movement can be performed with every 
A6 '05 key.
– Safety branch for the steering lock of the control 
unit for access and start 
authorisation:
In addition to the switch-offs in the control unit 
for access and start authorisation, the voltage 
supply for the motor of the electromechanical 
steering lock is interrupted in the switch for 
access and start authorisation in order to 
prevent the steering column locking 
automatically. 
If terminal 15 is switched on, the voltage supply 
is always switched off.
326_066
326_067
Switch for access and start authorisation E415
ULock
326_122Emergency release  
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– Reading in position P of the automatic 
transmission from the switch for gearbox 
position P F305:
The signal is used to activate the integrated, 
magnetic ignition key anti-removal lock. If the 
vehicle battery is flat, the key can be removed by 
pressing the mechanical emergency release.
– Reading in the information from the button for 
access and start authorisation E408 (only for 
vehicles with Advanced Key):
Fo r  s a fe t y  r e as o n s ,  t h e  p o s i t i o n s  o f t h e  b u t to n  fo r  
access and start authorisation are evaluated by 
the switch for access and start authorisation.
–
– Reading in the information from the antenna for 
central locking and anti-theft warning 
system R47:
The switch for access and start authorisation 
passes the data, which the vehicle key sends via 
remote control, on to the control unit for access 
and start authorisation. The control unit 
evaluates the data. 
– Reading in the signal from the brake light 
switch F (only for vehicles with Advanced Key):
To start the vehicle using the button for access 
and start authorisation, the brake pedal must be 
actuated. 
– Exchanging data with the key using the 
integrated read coil:
If a key is inserted into the switch for access and 
start authorisation (= S contact on), the 
electronics system transmits electric power into 
the key via the read coil. The key then sends the 
key identification into the switch via the 
transponder and the read coil. This sends the 
information to the control unit for access and 
start authorisation.
Convenience electrics
326_069 326_068
326_065  
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The electromechanical steering column lock was 
integrated into the control unit for access and start 
authorisation. 
Functions
– Terminal control:
The control unit for access and start 
authorisation puts the information about 
terminal 15, 75x, 50, S and P on 
CAN Convenience. 
The control unit also activates the relays for 
terminal 15 and 75x and passes the start request 
signal on to the engine control unit.– Locking the steering column:
The motor and gears for locking the steering 
column are integrated into the control unit for 
access and start authorisation. 
The position of the lock is checked using two 
integrated micro switches. Terminal 15 is only 
switched on after the steering is unlocked fully.
– Immobiliser and component protection:
The control unit is the master for these 
functions. 
Control unit for access and start authorisation J518
326_095  
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– CAN Communication:
The control unit is a participant on 
CAN Convenience. Data exchange between all 
the components of the access and start 
authorisation system is performed via the 
control unit. 
It is also the diagnosis interface for the 
components involved. All data, e.g. code, 
immobiliser data, etc. is stored in the control unit 
for access and start authorisation.
– Reading in the P/N signal from the control unit 
for automatic transmission J217:
The signal is used to activate the displays 
relating to engine start in dash panel insert J285.
Convenience electrics
326_062326_063
SELECT 
N OR P
TO START
THE ENGINE SELECT 
N OR P
START THE
ENGINE