1999 AUDI A4 sensor

24-122

- Start engine.


Specification: approx. battery voltage,
possibly fluctuating

Notes:

At certain operating points, the ECM "pulses"
the Ground (GND) for oxygen sensor heating.
This means that the Ground (GND) is
constantly switched on and off at these points.
It is therefore possible that the voltage
displayed on the tester will fluctuate.
It is possible to observe the ECM switching
oxygen sensor heating on and off within the
function "read measuring value block", display
group numbers 041 and 042.
If there is no voltage:

- Connect multimeter for voltage measurement as follows:Harness connector
Terminal
Measure to
1 (B+) Vehicle Ground (GND)
- Operate starter briefly.
Pa
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11/23/2002 htt
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Specification: approx. battery voltage
Pa
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24-123
If there is no voltage again:

- Check wire connection from terminal 1 to Fuel
Pump (FP) relay via fuse for open circuit.

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

If there is no voltage: - Connect multimeter for voltage measurement as follows:Harness connector
Terminal
Measure
to
2 (Ground -GND- activation of Engine Control Module -
ECM-) B+
- Start engine.

Specification: approx. battery voltage, possibly fluctuating
- Switch ignition off.
- Connect VAG1598/31 test box at wiring harness to ECM, do not
connect ECM Page 24
-17
.
Pa
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11/23/2002 htt
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24-124


- Check the following wire connection for open circuit:
Oxygen Sensor (O2S) heater -Z19- bank 1 before catalytic converter:
Harness connector
Terminal
VAG1598/31 test box
Socket
2 5
Oxygen Sensor (O2S) heater -Z28- bank 2 before catalytic converter:
Harness connector
Terminal
VAG1598/31 test box
Socket
2 4
Oxygen Sensor (O2S) heater -Z29- bank 1 behind catalytic converter:
Harness connector
Terminal
VAG1598/31 test box
Socket
2 63
Oxygen Sensor (O2S) heater -Z30- bank 2 behind catalytic converter:
Harness connector
Terminal
VAG1598/31 test box
Socket
2 6
Pa
ge 60 of 63 Ox
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en sensor control, checkin
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11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
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pair&id=AUDI.B5.FU05.24.3

24-125
If no malfunctions are found in wires:

- Replace appropriate Oxygen Sensor (O2S).

- Read readiness code Page 01
-78
. If DTC
memory was erased, readiness code must be
re-generated Page 01
-82
.
Pa
ge 61 of 63 Ox
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11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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pair&id=AUDI.B5.FU05.24.3

24-126

Oxygen sensor, removing and installing


Special tools and equipment

Removing
Component location of harness connectors Overview of component
locations, page Page 24
-5
3337 wrench, 7-piece set Locking compound G 052 112 A3
- Disconnect 4-pin harness connector leading to respective oxygen
sensor.
- Open cable ties.
- Unscrew oxygen sensor using special tool 3337.
Pa
ge 62 of 63 Ox
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11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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pair&id=AUDI.B5.FU05.24.3

24-127

Installing
Note the following when installing:

Notes:

Oxygen sensor threads are coated with an
assembly paste. This paste must not contact
sensor openings.
Cable ties must always be installed again in
exactly the same place to prevent the sensor
wire from contacting the exhaust pipe.
Tightening torque: 55 Nm
Pa
ge 63 of 63 Ox
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en sensor control, checkin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.3