AUDI A4 1998 B5 / 1.G ATW Engine Oxygen Sensor Control Owner's Guide

24-101


Note:
At higher temperatures, resistance climbs sharply.
If specified value is not obtained:
If specified value is obtained:
Checking voltage supply for oxygen sensor heating - Connect multimeter between terminal 1 and 2 for resistance
measurement.

Specified value at room temperature: 1 to 5
- Replace Oxygen Sensor (O2S).
- Check voltage supply of oxygen sensor heating Page 24
-101
.

- Connect multimeter between terminal 1 (B+) and 2 (Ground -GND-) for
voltage measurement.
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24-102

- Start engine.


Specification: approx. battery voltage,
possibly fluctuating

Note:

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.
When the ECM switches oxygen sensor heating
on and off can be observed, if necessary, via
the function "read measuring value block"
display group number 041.
If there is no voltage:

- Connect multimeter for voltage measurement as
follows:

Harness connector
Terminal
Measure to
1 (B+) Vehicle Ground (GND)
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- Operate starter briefly.


Specification: approx. battery voltage
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24-103
If there is no voltage again:

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

Electrical Wiring Diagrams, Troubleshooting &
Component Locations 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 Engine Control
Module (ECM), do not connect ECM Page 24
-19
.
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24-104


Oxygen Sensor (O2S) heater -Z19- for oxygen sensor before catalytic
converter:
Oxygen sensor heater 1 -Z29- for oxygen sensor behind catalytic
converter:
If wire connection is OK, but there is no Ground (GND) supply for oxygen
sensor heating: - Check following wire connection for open circuit:Harness connector
Terminal
VAG1598/31 test box
Socket
2 5
Harness connector
Terminal
VAG1598/31 test box
Socket
2 63
- Repair open circuit if necessary.
- Replace Engine Control Module (ECM) Page 24
-23
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24-105

Oxygen sensor, removing and installing


Special tools and equipment

3337 wrench, 7-piece set
Locking compound G 052 112 A3

Procedure

Note:
Coolant reservoir screws must be removed and coolant reservoir must be
placed to side in order to access harness connectors. The coolant hoses
can remain connected. - Disconnect 4-pin harness connector of oxygen sensor and lay it to
side.
1 - (brown) for Oxygen Sensor (O2S) behind Three Way Catalytic
Converter (TWC) -G130-
2 - (black) for Heated Oxygen Sensor (HO2S) -G39- before catalytic
converter
- Unscrew oxygen sensor using special tool 3337.
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24-106
When installing:

Note:

Oxygen sensor threads are coated with an
assembly paste. This paste must not contact
sensor openings.
Tightening torque: 55 Nm
Cable of oxygen sensor must always be
secured in the same position when installing so
that contact with the exhaust pipe is avoided.
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