wiring AUDI A4 1998 B5 / 1.G APB Engine Ignition System Checking

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Safety precautions

To prevent injuries to persons and/or damage to
the fuel injection and ignition system, the
following must be noted:

WARNING!

Be alert when working on or near the engine.
High ignition secondary voltage can cause
serious personal injury and damage vehicle
components.

DO NOT touch or disconnect ignition wiring
when the engine is running or being turned
at starter speed.
DO NOT operate the starter if fuel injectors
are removed.
Always switch off the ignition before
connecting or disconnecting the battery,
otherwise the engine control module may be
damaged.
The ignition must be switched off before
connecting or disconnecting injection or
ignition system wiring or tester cables.
In order to run the engine at starting speed
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If malfunction remains at the same cylinder.

- Disconnect harness connector from ignition
coil.

Electrical Wiring Diagrams, Troubleshooting & Component Locations
If the Ground (GND) connection is OK. - Check Ground (GND) connection between socket 4a and engine
Ground (GND) for open circuit and short circuit to B+. - Repair any open/short circuit as necessary.
- Connect hand-held multimeter (voltage range) to terminal 15 of
harness connector and Ground (GND).
- Disconnect harness connector from fuel injector of cylinder to be
tested.
- Operate starter.
Specified value: approx. battery voltage
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If the specification is not obtained:

- Check wiring.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations If the specification is obtained:

- Disconnect 3-pin harness connectors on power
output stages for ignition coils; component
locations overview Page 24
-5 .

- Then connect diode test lamp to 3-pin
connectors for both output stages.

If the specifications are not obtained: - Connect diode test lamp VAG1527 to following contacts on connectors
for power output stages: 3-pin harness connector
terminal
Specification
(with starter activated)
1 + Ground (GND) Diode test lamp should
2 + Ground (GND) light up
3 + Ground (GND)
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Check the following wiring connections for open circuits and/or short to B+
or Ground (GND).
Black 3-pin connector on power
output stage, terminal
3-pin connector on ignition
coil, terminal
1 1 (cylinder 1)
2 1 (cylinder 2)
3 1 (cylinder 3)
Brown 3-pin connector on power
output stage, terminal
3-pin connector on ignition
coil, terminal
1 1 (cylinder 4)
2 1 (cylinder 5)
3 1 (cylinder 6)
- Eliminate any open/short circuit as necessary.
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- Disconnect 4-pin harness connectors on power
output stages Component locations overview,
Page 24
-5 .

- Connect diode test lamp VAG1527 in turn to the following contacts on
the two 4-pin connectors for the power output stages.
- Then, operate starter for a few seconds.
6-pin connector on wiring harness,
terminal
Specification
1 + Ground (GND) Diode test lamp
should
3 + Ground (GND) flash (brief impulse)
4 + Ground (GND)
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If the specifications are not obtained:

- Switch ignition off.

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

The following wiring connections are to be checked for open circuits
and/or short to B+ or Ground (GND).
Black 4-pin connector on wiring
harness, terminal VAG1598/31 test box,
socket
1 94
3 110
4 102 Brown 4-pin connector on wiring
harness, terminal VAG1598/31 test box,
socket
1 95
3 111
4 103
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- Rectify any open/short circuit as necessary.
If no wiring malfunction is detected:

- Connect 4-pin connectors to power output
stages.

- Disconnect 3-pin connectors from power output
stages.

- Connect diode test lamp VAG1527 to battery
(B+) and to one of the 3 terminals on power
output stage.

- Operate starter for few seconds.

The diode test lamp should flash.

- Carry out test with all 3 terminals on each of the
3-pin connectors for the power output stages.

The diode test lamp should flash each time.
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- If diode test lamp does not light up, test for open
circuit in wiring using wiring diagram.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
If the diode test lamp lights up:

- Replace power output stage.

Note:
Before installing new power output stage coat
metal side with heat paste (part no. G 052 170
A1). The heat paste is used to prevent corrosion
between the power output stage and the
fastening point, it is also used to transfer heat
from the power output stage.

CAUTION!

Part numbers are only for reference, always
check with your parts department for latest
information.
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Display fields

1 2 3 4
Display Group 004: Intake air temperature with engine idling
Display xxxx rpm xx.xxx V
xxx.x C
xxx.x C
Indicates Engine speed Battery voltage Coolant temperature
Intake air temperature
Work range min.: 750 RPM
max.: 6800 RPM min.:10.000 V
max.: 15.000 V min.: -48.0 C
max.: 143.0 C
min.: -48.0 C
max.: 143.0 C
Specified value xxxx RPM 12.000...15.000 V
80.0...110.0 C
Between ambient temp. and 120 C
1)
1) If there is a large difference between the temperature displayed and the ambient temperature at the sensor, check the
sensor and sensor wiring for contact resistance and open circuit.
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Checking wiring:

- Switch ignition off.

- Connect test box VAG1598/31 to wiring harness
for engine control module. Do not connect to the
engine control module itself. Page 24
-20
.

- Check for open circuit in wiring between test box and 2 pin harness
connector using wiring diagram.

Specified value: max. 1.5
Terminal on 2-pin harness
connector
Contact on control module
connector or test box
1
2 85
108
- Check wiring for short circuits to each other between contacts 1 and 2
on 2-pin connector. Also test for short circuits to B+ or Ground (GND).
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