2003 AUDI A8 relay

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The wide range of sensors permits detection
not only of head-on collision and side impact,
but also of rear-end collisions. Use is made in the Audi A8 ´03 of the 8.4E+
airbag system with the aim of attaining greater
occupant safety whilst reducing the impact.
This was achieved, for example, by way of two-
stage front airbag triggering, active front head
restraints and a battery cut-off element.
K75 Airbag warning lamp
K145 Airbag disabled warning lamp,
front passenger side
N95 Driver side airbag igniter
N131 Airbag igniter 1, front passenger side
N153 Belt tensioner igniter 1, driver side
N154 Belt tensioner igniter 2,
front passenger side
N196 Rear belt tensioner igniter,
driver side
N197 Rear belt tensioner igniter,
front passenger side
N198 Rear belt tensioner igniter,
centre
N199 Side airbag igniter, driver side
N200 Side airbag igniter,
front passenger side
N201 Rear side airbag igniter,
driver side
N202 Rear side airbag igniter,
front passenger side
N251 Curtain airbag igniter, driver side
N252 Curtain airbag igniter,
front passenger side
T16 16-pin connector
(diagnostic connection) Key
E24 Driver side belt switch
E25 Front passenger side belt switch
E224 Airbag disabling key switch,
front passenger side
G85 Steering angle sender
G179 Side airbag crash sensor,
driver side (B-pillar)
G180 Side airbag crash sensor,
front passenger side (B-pillar)
G256 Rear side airbag crash sensor,
driver side
G257 Rear side airbag crash sensor,
front passenger side
G283 Front airbag crash sensor,
driver side
G284 Front airbag crash sensor,
front passenger side
J234 Airbag control unit
J285 Control unit with display
in dash panel insert
J393 Convenience system central
control unit
J526 Telephone/telematics control unit
J533 Data bus diagnostic interface
(gateway)
J623 Engine control unit
J655 Battery cut-off relay

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15
J234
J655
1
2
E224
3
G283G284G179
N131
F138
N202N199N200N201N95
Key
E24 Driver side belt switch
E25 Front passenger side belt switch
E224 Airbag disabling key switch,
front passenger side
F138 Airbag coil connector/return spring
with slip ring
G179 Side airbag crash sensor,
driver side
G180 Side airbag crash sensor,
front passenger side
G256 Rear side airbag crash sensor,
driver side
G257 Rear side airbag crash sensor,
front passenger side
G283 Front airbag crash sensor,
driver side
G284 Front airbag crash sensor,
front passenger side
Block diagram
Passenger Protection
J234 Airbag control unit
J655 Battery cut-off relay
N95 Driver side airbag igniter
N131 Airbag igniter 1, front passenger side
N153 Belt tensioner igniter 1, driver side
N154 Belt tensioner igniter 2,
front passenger side
N196 Rear belt tensioner igniter, driver side
N197 Rear belt tensioner igniter,
front passenger side
N198 Rear belt tensioner igniter, centre
N199 Side airbag igniter, driver side
N200 Side airbag igniter,
front passenger side
N201 Rear side airbag igniter,
driver side
N202 Rear side airbag igniter,
front passenger side

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Passenger Protection
15 30
+
-
31
J644
J655
43
B
1
2
A
TerminalPinInput/outputDescription
30, battery A Input
(screw connection)U
bat. term. 30/battery
87 B Output
(screw connection)Output
Terminal 15 1 Input
(plug connection)Positive power supply,
interruptible
Vehicle earth 2 Input
(plug connection)Earth from
airbag control unit J234
Crash signal 3 Input
(plug connection)Crash signal from
airbag control unit J234
Diagnosis 4 Input
(plug connection)Diagnostic wire from
airbag control unit J234
Battery cut-off relay J655
The battery cut-off relay is a battery isolating
element designed to disconnect starter and
alternator power from the electrical system in
the event of a crash.
Block diagram
J644 Energy management control unit
J655 Battery cut-off relay
SSP282_076

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Fitting location
The battery cut-off relay is located in front of
the battery.
Triggering
The airbag control unit J234 provides the
battery cut-off element with the triggering
command via a discrete wire.
Triggering of this element by the airbag
control unit causes a white panel to appear in
the element window instead of a copper coil.
Following isolation, the battery cut-off
element can be manually reset by way of the
yellow knob.
Control element test
The control element test in the airbag control
unit also triggers the battery cut-off relay. It
should be ensured that the relay is manually
reset, as otherwise the battery cannot be
charged.
SSP282_079
SSP282_077
SSP282_083
Reset knobWindow

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Hot-film air-mass meter G70
Engine speed sender G28
Hall sender G40 (bank 2) and
Hall sender 2 G163 (bank 1)
Lambda probe G39
(bank 1)
Lambda probe II G108
(bank 2)
Lambda probe after catalyst G130
(bank 1)
Lambda probe II after catalyst G131
(bank 2)
Throttle valve control
part J338 with
Throttle valve drive G186
(electric power control)
Throttle valve drive angle sender 1 G187
Throttle valve drive angle sender 2 G188
Coolant temperature sender G62
Knock sensor I G61 (bank 1) and
Knock sensor II G66 (bank 2)
Additional signals:
– Air conditioner requirement
– Cruise control switch
– Term. 50, stage 1
– Automatic gearbox selector lever positionEngine control unit J623
Steering
angle sender G85
ESP
control unit J104
Dash panel
insert CANAutomatic
gearbox
control unit J217
Airbag
control unit J234Intake manifold changeover valve
N156 and
Intake manifold changeover valve 2
N261
Left electrohydraulic engine mounting
solenoid valve N144 and
Right electrohydraulic engine mounting
solenoid valve N145
Torque rod valve N382
Lambda probe heater Z19
(bank 1) and
Lambda probe 2 heater Z28
(bank 2)
Lambda probe 1 heater
after catalyst Z29
Lambda probe 2 heater
after catalyst Z30
Additional signals:
– Starter relay term. 50, stage 2
– Tank leakage pump (USA only)
– Air conditioner compressor (out)Fuel pump relay J17
Fuel pump G6
Fuel pump II relay J49
Fuel pump G23
Injectors N30, N31, N32, N33 (bank 1)
Injectors N83, N84, N85, N86 (bank 2)
Ignition coils N (no. 1 cyl.), N128 (no. 2 cyl.),
N158 (no. 3 cyl.), N163 (no. 4 cyl.)
Ignition coils N164 (no. 5 cyl.), N189 (no. 6 cyl.),
N190 (no. 7 cyl.), N191 (no. 8 cyl.)
Activated charcoal filter system solenoid
valve 1 N80
Secondary-air pump relay J299 and
Secondary-air pump motor V101
Secondary air inlet valve N112
Throttle valve control part J338
With throttle valve drive G186
Inlet camshaft timing adjustment valve 1
N205 (bank 1)
and
N208 (bank 2) Pedal position sender/accelerator
pedal module with accelerator pedal
position sender G79 and accelerator
pedal position sender 2 G185
Brake light switch F and
Brake pedal switch F47
Clutch pedal switch F36
(manual gearbox only)
Control unit with display in dash
panel insert J285Data bus diagnostic
interface J533
Engine, Mechanics
System layout
Actuators/sensors
SSP282_091 Drive system CAN
Diagnosis CAN

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Hot-film air-mass meter G70
Engine speed sender G28
Hall sender G40 (bank 2) and
Hall sender 2 G163 (bank 1)
Lambda probe G39
(bank 1)
Lambda probe II G108
(bank 2)
Lambda probe after catalyst G130
(bank 1)
Lambda probe II after catalyst G131
(bank 2)
Throttle valve control
part J338 with
Throttle valve drive G186
(electric power control)
Throttle valve drive angle sender 1 G187
Throttle valve drive angle sender 2 G188
Coolant temperature sender G62
Knock sensor I G61 (bank 1) and
Knock sensor II G66 (bank 2)
Additional signals:
– Air conditioner requirement
– Cruise control switch
– Term. 50, stage 1
– Automatic gearbox selector lever positionEngine control unit J623
Steering
angle sender G85
ESP
control unit J104
Dash panel
insert CANAutomatic
gearbox
control unit J217
Airbag
control unit J234Intake manifold changeover valve
N156 and
Intake manifold changeover valve 2
N261
Left electrohydraulic engine mounting
solenoid valve N144 and
Right electrohydraulic engine mounting
solenoid valve N145
Torque rod valve N382
Lambda probe heater Z19
(bank 1) and
Lambda probe 2 heater Z28
(bank 2)
Lambda probe 1 heater
after catalyst Z29
Lambda probe 2 heater
after catalyst Z30
Additional signals:
– Starter relay term. 50, stage 2
– Tank leakage pump (USA only)
– Air conditioner compressor (out)Fuel pump relay J17
Fuel pump G6
Fuel pump II relay J49
Fuel pump G23
Injectors N30, N31, N32, N33 (bank 1)
Injectors N83, N84, N85, N86 (bank 2)
Ignition coils N (no. 1 cyl.), N128 (no. 2 cyl.),
N158 (no. 3 cyl.), N163 (no. 4 cyl.)
Ignition coils N164 (no. 5 cyl.), N189 (no. 6 cyl.),
N190 (no. 7 cyl.), N191 (no. 8 cyl.)
Activated charcoal filter system solenoid
valve 1 N80
Secondary-air pump relay J299 and
Secondary-air pump motor V101
Secondary air inlet valve N112
Throttle valve control part J338
With throttle valve drive G186
Inlet camshaft timing adjustment valve 1
N205 (bank 1)
and
N208 (bank 2) Pedal position sender/accelerator
pedal module with accelerator pedal
position sender G79 and accelerator
pedal position sender 2 G185
Brake light switch F and
Brake pedal switch F47
Clutch pedal switch F36
(manual gearbox only)
Control unit with display in dash
panel insert J285Data bus diagnostic
interface J533
Engine, Mechanics
System layout
Actuators/sensors
SSP282_091 Drive system CAN
Diagnosis CAN

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Engine, Mechanics
Sequence of operations
1 Entry and start authorisation switch E415/entry and start authorisation button E408
2 Entry and start authorisation control unit J518
The entry and start authorisation control
unit checks for authorisation – in the form
of information on selector slide position N
or P – from the automatic gearbox control
unit J217 and for brake application in the
case of a start signal from the entry and
start authorisation button E408.
3 Engine control unit J623 Application of selector slide position P/N or
"clutch pressed" information to the engine
control unit (separate interface) causes the
two starter relays J53 and J695 to be
actuated simultaneously. The relays then
switch terminal 50 for starter actuation.
The starter operates and cranks the engine.
On exceeding a defined engine speed, the
engine control unit J623 recognises that
the engine has started and the relays are
deenergised (thus terminating starting
process).
As a safeguard, two relays are connected in
series. In the event of fusion welding of the
make contacts (relay remains closed
following deenergisation), the engine
control unit J623 can thus interrupt the
circuit (terminal 50) by way of the other
relay in each case.
The two relays are deenergised alternately
in order to ensure even make contact wear
(break spark) in both relays. The
deenergisation sequence alternates. The driver triggers a brief start signal
(min. 20 ms) by turning the ignition key to
start position or by pressing the entry and
start authorisation button E408.
If the start prerequisites have been
satisfied, the entry and start authorisation
control unit J518 transmits a start request
– terminal 50 ON – to the engine control
unit J623.
The entry and start authorisation control unit J518 also controls the terminal 15 and
terminal 75x circuits.
Relay operation is monitored and faults diagnosed by evaluating the alternating
deenergisation with the aid of the terminal
50R interface.
The terminal 50R interface represents a link
with terminal 50 and provides the engine
control unit J623 with feedback for start
control/diagnosis.
Automatically controlled starting is not
permitted in the event of undervoltage or a
system fault.
The engine can however be started
manually by way of corresponding start
signal actuation.
To relieve the load on the starter and
battery, the relay actuation time is
limited to approx. 10 seconds per starting
operation (automatic or manual starting).

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D1
30
15
J329J53J695J694
75xE415
N376
6x
J623
J518
50R
50R
3
12
12
E408
STOP START
58s
210 210
D1 Inhibitor reading unit
E408 Entry and start authorisation button
E415 Entry and start authorisation switch
J53 Starter motor relay
J329 Terminal 15 voltage supply relay
J518 Entry and start authorisation
control unit Block diagram
SSP282_024
Colour code
= Input signal
= Output signal
= Positive supply
= Earth
J623 Engine control unit
J694 Terminal 75x voltage supply relay
J695 Starter relay 2
N376 Ignition key withdrawal lock magnet
Additional signals
F - Brake light switch
Manual gearbox -> F194
Clutch pedal switch
Automatic gearbox -> Selector lever
position from automatic gearbox
control unit J217
Terminal 50/starter
1
2
3