1997 AUDI A4 sensor

24-95

Continuation
If specified value in display field 3 and 4 is not
obtained:

- Road test vehicle in order to free oxygen sensor
of possible residue and repeat test.
If specified value in display field 3 and 4 is not
obtained, even after road test:

- Replace Heated Oxygen Sensor (HO2S) -
G39-.

Note:
If oxygen sensor voltage is OK and dwell time of
oxygen sensor control behind catalytic converter
is still above 1200 ms, even after a road test, this
suggests aging of the oxygen sensor before
catalytic converter.
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24-96

Checking primary voltage

Note:
Coolant reservoir screws must be removed and coolant reservoir must be
placed to side in order to access the harness connector. The coolant
hoses can remain connected. - Disconnect 4-pin harness connector -1- (brown) to Oxygen Sensor
(O2S) behind Three Way Catalytic Converter (TWC) -G130-.

If specified value is not obtained:
If specified value is obtained: - Connect multimeter between terminal 3 and 4 for voltage
measurement.
- Switch ignition on.

Specification: 0.400 to 0.500 V
- Switch ignition off.
- Check oxygen sensor wiring.
- Replace Oxygen Sensor (O2S) behind Three Way Catalytic Converter
(TWC) -G130-.
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24-97

Checking oxygen sensor wires

Note:
Coolant reservoir screws must be removed and coolant reservoir must be
placed to side in order to access the harness connector. The coolant
hoses can remain connected. - Disconnect 4-pin harness connector -1- (brown) to Oxygen Sensor
(O2S) behind Three Way Catalytic Converter (TWC) -G130-.
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.

- Check following wire connections for open circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
3 68
4 69
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24-98

- Repair open circuit if necessary.

- Check wires to each other for short circuit.
If wire connection is OK:

- Replace Engine Control Module (ECM) Page
24
-23

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24-99


Oxygen Sensor (O2S) heater -Z19- and
oxygen sensor heater 1 -Z29- for oxygen
sensor before catalytic converter and
oxygen sensor behind catalytic converter,
checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
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24-100

Test requirements:

Coolant Temperature at least 80 C.

Fuse for oxygen sensor heating OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

Test sequence

or
Note:
Coolant reservoir screws must be removed and coolant reservoir must be
placed to side in order to access the harness connector. The coolant
hoses can remain connected. - Disconnect 4-pin harness connector -2- (black) to Heated Oxygen
Sensor (HO2S) -G39- before catalytic converter.
- Disconnect 4-pin harness connector -1- (brown) to Oxygen Sensor
(O2S) behind Three Way Catalytic Converter (TWC) -G130-.
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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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pair&id=AUDI.B5.FU06.24.2