1998 AUDI A4 wiring diagram

24-117

Checking voltage supply for oxygen sensor
heater
Component location of 4-pin harness connector
of oxygen sensors Page 24
-5 .

- Check fuse for oxygen sensor heater

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
- Disconnect 4-pin harness connector of particular
oxygen sensor.

If there is no voltage reading: - Connect hand-held multimeter (voltage measurement range) between
sockets 1 (B+) and 2 (Ground (GND)) using test leads from VAG1594
connector test kit.
- Operate starter briefly.
Specified value: approx. battery voltage
- Connect hand-held multimeter (voltage measurement range) between
socket 1 (B+) and vehicle Ground (GND) using test leads from
VAG1594 connector test kit.
Pa
ge 45 of 61 Ox
yg
en sensor control, checkin
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.2

24-118

- Operate starter briefly.

Specified value: approx. battery voltage
If there is still no voltage reading:

- Check for open circuit and/or short circuit in
wiring between fuel pump relay and socket 1 on
the relevant oxygen sensor connector (on wiring
harness) via fuse.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations If the voltage supply is OK:

- Connect hand-held multimeter (voltage measurement range) between
socket 2 (switched Ground (GND) connection from engine control
module) and B+ terminal using test leads from VAG1594 connector test
kit.
Pa
ge 46 of 61 Ox
yg
en sensor control, checkin
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.FU04.24.2

24-120

Heated Oxygen Sensor (HO2S) -G39
Connector on wiring
harness, socket
VAG1598/31 test
box, socket
2 5 (Ground)
Heated Oxygen Sensor (HO2S) 2 -G108
Connector on wiring
harness, socket
VAG1598/31 test
box, socket
2 4 (Ground)
Oxygen Sensor (O2S) Behind Three Way
Catalytic Converter (TWC) -G130
Connector on wiring
harness, socket
VAG1598/31 test
box, socket
2 63 (Ground)
Oxygen Sensor (O2S) 2 Behind Three Way
Catalytic Converter (TWC) -G131
Connector on wiring
harness, socket
VAG1598/31 test
box, socket
2 6 (Ground)
Resistance in wiring: max. 1.5 Ohm

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
Pa
ge 48 of 61 Ox
yg
en sensor control, checkin
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.FU04.24.2

24-123
If Specified value is obtained:

- Replace relevant oxygen sensor.

Checking oxygen sensor wiring for Heated
Oxygen Sensor (HO2S) -G39
Component location of 4-pin harness connector
of oxygen sensor Page 24
-5 .

- Disconnect 4-pin connector (black) for Heated
Oxygen Sensor (HO2S) -G39.

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

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Check following wiring connections for open circuits:
Connector on wiring harness,
socket
VAG1598/31 test box socket

3 51
4 70
Resistance in wiring: max. 1.5 Ohm
Pa
ge 51 of 61 Ox
yg
en sensor control, checkin
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.FU04.24.2

24-124


Electrical Wiring Diagrams, Troubleshooting & Component Locations
Electrical Wiring Diagrams, Troubleshooting & Component Locations
If no malfunction is identified in the wiring: - Check wiring also on 4-pin harness connector for short circuits to each
other.
Connector on wiring harness,
socket
VAG1598/31 test box socket

4 51
Specified value: infinite ohms (open circuit)- Check shielded wire for short circuit to sensor wiring.
Connector on wiring harness,
socket
VAG1598/31 test box socket

4 32
3 32
Specified value: infinite ohms(open circuit)- Replace Motronic Engine Control Module (ECM) -J220 Page 24
-24
.
Pa
ge 52 of 61 Ox
yg
en sensor control, checkin
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.FU04.24.2

24-125

Checking wiring for Oxygen Sensor (O2S)
Behind Three Way Catalytic Converter (TWC)
-G130
Component location of 4-pin harness connector
of oxygen sensor Page 24
-5 .

- Disconnect 4-pin connector (black) for Oxygen
Sensor (O2S) Behind Three Way Catalytic
Converter (TWC) -G130.

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

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Check following wiring connections for open circuits:
Connector on wiring harness,
socket
VAG1598/31 test box socket

3 68
4 69
Resistance in wiring: max. 1.5 ohm
Pa
ge 53 of 61 Ox
yg
en sensor control, checkin
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.FU04.24.2

24-126


Electrical Wiring Diagrams, Troubleshooting & Component Locations
Electrical Wiring Diagrams, Troubleshooting & Component Locations
If no malfunction is identified in the wiring: - Check wiring also on 4-pin harness connector for short circuits to each
other.
Connector on wiring harness,
socket
VAG1598/31 test box socket

4 68
Specified value: infinite ohms (open circuit)- Check shielded wire for short circuit to sensor wiring.
Connector on wiring harness,
socket
VAG1598/31 test box socket

4 32
3 32
Specified value: infinite ohms (open circuit)- Replace Motronic Engine Control Module (ECM) -J220 Page 24
-24
.
Pa
ge 54 of 61 Ox
yg
en sensor control, checkin
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.FU04.24.2

24-127

Checking wiring for Heated Oxygen Sensor
(HO2S) 2 -G108
Component location of 4-pin harness connector
of oxygen sensor Page 24
-5 .

- Disconnect 4-pin connector (black) for Heated
Oxygen Sensor (HO2S) 2 -G108.

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

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Check following wiring connections for open circuits:
Connector on wiring harness,
socket
VAG1598/31 test box socket

3 12
4 13
Resistance in wiring: max. 1.5 ohm
Pa
ge 55 of 61 Ox
yg
en sensor control, checkin
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.FU04.24.2