wiring AUDI A4 1999 B5 / 1.G APB Engine Motronic Multiport Fuel Injection System Servising Workshop Manual

24-1


Motronic Multiport Fuel
Injection (MFI) system,
servicing

Safety precautions


Observe following precautions if test and
measuring instruments are required during a
road test:

WARNING!

During a road test in an airbag equipped
vehicle, test equipment must always be
fastened to and operated from the rear seat
by a second technician.
When driving or riding in an airbag equipped
vehicle, NEVER hold the scan tool or other
test equipment in your hands or lap while in
motion. Objects between you and and the
airbag increase the risk of injury in an
accident.

To prevent injuries to persons and/or damage
to the fuel injection and ignition system, the
following must be noted:
Always switch off the ignition before
connecting or disconnecting injection or
ignition system wiring or tester cables.
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24-20

Wiring and component check with
VAG1598/31 test box


Notes:

The VAG1598/31 test box is designed so it can
be simultaneously connected to the control
module wiring harness and to the control
module itself.
This has the advantage of enabling the engine
management system to remain fully operational
even with the test box connected (for example,
when testing signals while the engine is
running).
The instructions for performing the individual
tests indicate whether or not the engine control
module itself also needs to be connected to the
test box.
Use the hand multimeter Fluke 83 (or
equivalent) or the multimeter VAG1715 and the
diode test lamp VAG1527 for the checks.
To connect the testers to VAG1598/31 test box,
always use the adapter leads from VAG1594 A
connector test kit.

Required special tools and test equipment
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24-22


After installing the engine control module, carry out the following
operation
Note:
At the first learning (adaptation) phase during the "Engine-Basic Setting"
the engine might run a little rough at idle and bucks/jerks a little while
driving. - Connect VAG1598/31 test box to wiring harness connector. Also
connect the Ground (GND) clamp from test box to Ground (GND). The
instructions for performing the individual tests indicate whether or not
the engine control module itself also needs to be connected to the test
box.
- Carry out test as described in the relevant repair instructions.
- Check DTC memory and erase if necessary Page 01
-15
.
- Generate new readiness code Page 01
-105
.
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24-40

Checking voltage supply

Test conditions

Fuse for injectors OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

- Disconnect harness connector from fuel injector
to be tested.

- Connect diode test lamp (for measuring voltage) between Ground
(GND) and socket 1 of connector.
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24-41

- Switch ignition on. The diode test lamp should
light up.

- If diode test lamp does not light up, test for open
circuits in wiring between contact 1 and fuse for
injectors. If necessary, rectify open circuit.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
- If diode test lamp lights up, test activation of
injectors.

C - Testing activation of injectors

- Remove plug connector from the injector which
is to be tested.

Specified value: the diode test lamp should start flashing.
Note:
Diode test lamps with a low current draw continue to glow faintly between - Connect diode test lamp VAG 1527 between the battery positive
terminal (+) and contact 2 on the connector.
- Operate starter for a few seconds (the engine can be allowed to start).
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24-42
If the diode test lamp does not flash:

- Connect test box VAG 1598/31 to wiring
harness for engine control unit. Do not connect
to the engine control unit itself. Page 24
-20
.

- Test for open circuit or short to B+ in wiring between engine control
module and contact 2 on harness connector for fuel injector being
tested.
Contact 2 on
connector for injector,
Cylinder No. Test box VAG 1598/31, socket
1 96
2 112
3 88
4 97
5 113
6 89
- Rectify short circuit or open circuit if necessary.
- If wiring is OK, install a new engine control module Page 24
-24
.
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24-47

- Lift fuel rail off intake manifold together with fuel
injectors and support the fuel rail.

Note:

After lifting off the fuel rail, check to make sure
that the injectors are properly secured to the
fuel rail.
It is possible that some of the fuel injectors will
become detached from the fuel rail and remain
in the intake manifold when the fuel rail is
removed. If this happens, install the fuel
injectors back onto the fuel rail Page 24
-53
.

WARNING!
Make sure test box is inside of passenger compartment. - Connect test box VAG 1598/31 to wiring harness for engine control
unit. Do not connect to the engine control module itself Page 24
-20
.
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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
.
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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.
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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.
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