1996 AUDI A4 relay

24-5


Component locations, overview

Components A to I are not shown in the exploded
drawing.
A - Brake Light Switch -F- and Brake Pedal
Switch -F47-
In footwell on pedal bracket near brake
pedal
B - Diagnostic connectorIn front knee protection, driver side
C - Fuel Pump (FP) relay -J17-Relay position 4 of central electrics left side
under dash panel
D - Clutch Vacuum Vent Switch -F36In footwell on pedal frame
E - Throttle Position (TP) Sensor -G79-
and Sender -2- for accelerator pedal
position -G185 In footwell on accelerator pedal (both
senders are installed in one housing)
Pa
ge 7 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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pair&id=AUDI.B5.FU04.24.1

24-9


12 -
Recirculating valve for turbocharger -
N249
13 -
Fuel pressure regulator
14 -
Camshaft Position (CMP) Sensor 2 -G163
Cylinder bank 2Previously identified as Camshaft Position
(CMP) Sensor 2 -G40
15 -
Secondary Air Injection (AIR) Pump Relay
-J299 Only on vehicles with automatic
transmission
16 -
Motronic Engine Control Module (ECM) -
J220
17 -
3-pin harness connector For Engine Speed (RPM) Sensor -G28grey
18 -
3-pin harness connector For Knock Sensor (KS) 2 -G66
19 -
Harness connector for Heated Oxygen
Sensor (HO2S) 2 -G108 and Oxygen
Sensor (O2S) Heater -Z28 4-pin black
Pa
ge 11 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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e=re
pair&id=AUDI.B5.FU04.24.1

24-33

Fuel pressure regulator and residual
fuel pressure, checking


Requirements

Fuel pump relay OK
Fuel pump OK
Fuel filter OK
Battery voltage at least 11 V

Note:
The fuel pressure regulator regulates the fuel
pressure according to intake manifold pressure.
This ensures that the drop in pressure at the
injectors remains the same throughout all engine
speed and engine load ranges.

WARNING!

Fire hazard! The fuel system is pressurized.
Before loosening hose connections or
opening the test connection (to measure fuel
pressure), place a cloth around the
connection. Then release pressure by
carefully pulling off the hose or cap.
Pa
ge 38 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-48

Checking for leaks

- Bridge sockets 1 and 65 on the test box using
test leads from VAG1594 A connector test kit.
(This creates an Ground (GND) connection to
one side of the fuel pump relay coil.)

Note:
Once the socket are bridged the fuel pump runs
continuously, even if the engine is not running.
This is because the fuel pump relay receives its
positive voltage supply via the central electrics.
The negative voltage supply for the fuel pump
relay comes via the cable bridge on the test box.

WARNING!

Fire hazard. DO NOT smoke or work near
heaters or have anything in the area that can
ignite fuel!

- Check injectors fuel for leaks (visual check).
When fuel pump is running, only 1 or 2 drops
should escape per minute from each injector.

- If fuel loss is greater, switch off fuel pump
(remove bridge) and replace faulty injector
Page 24
-53
, also observe notes on Page 24
-
53
.
Pa
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port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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e=re
pair&id=AUDI.B5.FU04.24.1

24-49


WARNING!
Make sure test box is inside of passenger compartment.
The fuel pump should run. - Connect one fuel injector terminal to engine Ground (GND) using test
cable and crocodile clamp from VAG1594 connector test kit.
- Connect second fuel injector terminal to B+ using remote control
VAG1348/3 A, adapter cable VAG1348/3-2 and auxiliary cable.
- Bridge sockets 1 and 65 on the test box using test leads from
VAG1594 A connector test kit. (This creates an Ground (GND)
connection to one side of the fuel pump relay coil.)
Pa
ge 59 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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e=re
pair&id=AUDI.B5.FU04.24.1

24-54

Fuel Pump (FP) relay -J17 and relay
activation, checking


Note:

The fuel pump relay is located in the central electrics in the left-hand
footwell, relay position 4.
A - Checking Fuel Pump (FP) relay -J17
- Remove storage bin in front left-hand footwell.

Electrical Wiring Diagrams, Troubleshooting & Component Locations
The fuel pump relay should pick up (can be felt and heard) and the diode
test lamp should light up. - Remove fuel pump fuse from fuse holder and connect diode test lamp
VAG1527 between Ground and one of the two contacts for the fuel
pump fuse. - Operate starter briefly.
- If fuel pump relay does not pick up, check activation Page 24
-56
.
Pa
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port Fuel In
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(MFI
) system, servicin
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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pair&id=AUDI.B5.FU04.24.1

24-55

- If fuel pump relay picks up but diode test lamp
does not light up, repeat test on other terminal.

Electrical Wiring Diagrams, Troubleshooting & Component Locations - If diode test lamp still does not light up, test for open circuit in wiring
between fuel pump fuse and terminal 23 in relay position 4. If
necessary, rectify open circuit. - If voltage supply, activation and wiring for fuel pump relay are OK,
install new fuel pump relay.
Pa
ge 65 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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pair&id=AUDI.B5.FU04.24.1

24-56

B - Checking voltage supply and activation of
fuel pump relay

Note:
Activation of the fuel pump relay can also be
tested using the final control diagnosis Page
01
-75
.

- Remove fuel pump relay -J17 from central
electrics, relay position 4.

Checking voltage supply

- Switch ignition on.

Specification: approx. battery voltage in each case
Electrical Wiring Diagrams, Troubleshooting & Component Locations - Connect hand-held multimeter VAG1526 between Ground (GND) and
relay panel contact 19 (B+; terminal 15 from ignition switch).
Disconnect, then re-connect between Ground (GND) and relay panel
contact 17 (permanent B+; terminal 30 from battery).
- If values are not as specified, rectify open circuit.
Pa
ge 66 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1