catalytic converter AUDI A4 1999 B5 / 1.G AWM Engine Oxygen Sensor Control Checking Workshop Manual

24-71


Oxygen sensor control,
checking Oxygen sensor and oxygen sensor control
before catalytic converter, checking

Special Tools and Equipment

VAG1526A
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
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Continuation
If specified value in display field 1 is not obtained
or if value does not fluctuate at least 2 %:

- Road test vehicle in order to free oxygen sensor
of possible residue and repeat test.
If specified value in display field 1 is not obtained
even after road test or if value does not fluctuate
at least 2 %:

- Check primary voltage Page 24
-81
.

- Test oxygen sensor heater before catalytic
converter Page 24
-89
.

- Check oxygen sensor before catalytic converter
for aging Page 24
-84
.
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24-80
Evaluation display group 033 Display field:
2
Possible cause
Corrective action
larger than
4.800 V
Short circuit to B+ in wire connections between
oxygen sensor and control module
Oxygen sensor faulty- Check oxygen sensor wires of oxygen sensor
before catalytic converter Page 24
-82

smaller than
0.130 V
Short circuit to Ground (GND) in wire connections
between oxygen sensor and control module
Oxygen sensor faulty
- Replace oxygen sensor before catalytic
converter
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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 6-pin harness connector (black) -2- to Heated Oxygen
Sensor (HO2S) -G39- before catalytic converter.

- Connect multimeter between terminal 1 and 5 for voltage
measurement.
- Switch ignition on.

Specification: 0.400 to 0.500 V
- Switch ignition off.
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If specified value is not obtained:

- Check oxygen sensor wiring.
If specified value is obtained:

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

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 6-pin harness connector (black) -2- to Heated Oxygen
Sensor (HO2S) -G39- before catalytic converter.
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.
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24-84

Oxygen sensor aging, oxygen sensor
before catalytic converter, checking


Special Tools and Equipment

VAG1788/10 RPM adjuster

Test requirement:
VAS5051 with VAG5051/1Coolant Temperature at least 80 C.
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24-89


Oxygen sensor heating, Oxygen Sensor
(O2S) Heater -Z19- before catalytic
converter, checking

Special Tools and Equipment

VAG1526A
VAG1594A
VAG1598/31
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24-90

Test requirements:

Coolant Temperature at least 80 C.

Fuse for oxygen sensor heating OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

Test sequence

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 6-pin harness connector (black) -2- to Heated Oxygen
Sensor (HO2S) -G39- before catalytic converter.

If specified value is not obtained: - Connect multimeter between terminal 3 and 4 for resistance
measurement.

Specified value at room temperature: 2.5 to 10
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24-94

Heated Oxygen Sensor (HO2S) and
oxygen sensor control after Three Way
Catalytic Converter (TWC), checking


Note:
The oxygen sensor before catalytic converter
(bank 1, sensor 1) regulates to Lambda 1. If this
oxygen sensor is damaged, e.g. due to soiling or
overheating, the regulation value may have
shifted. Deviations from Lambda 1 are detected
by the oxygen sensor after catalytic converter
(bank 1, sensor 2). If it recognizes the deviations
downward or upward, it influences the regulation
before catalytic converter, generally increasing or
decreasing it respectively.
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Display fields

1 2 3 4
Display group 030: Oxygen sensor status
Display X X X
X X X

Indicated Oxygen sensor status, bank 1, sensor 1
Oxygen sensor status bank 2, sensor 1

Functional range 0 = off
1 = on 0 = off
1 = on

Specified value 1 1 1
1 1 0

Note
If specified value is not obtained Page 24
-107

Significance of 3 digit indications in display group 030 X
X
X
Display fields 1 and 2
X Oxygen sensor control: 0= not active; 1 = active
X Operational readiness of oxygen sensor: 0= not active; 1 = active
X Condition of oxygen sensor heater: 0= not active; 1 = active
Notes:

The first position of the 3 digit indication (heating) fluctuates between 0 and 1.
Oxygen sensor control of oxygen sensor after catalytic converter (B1-S2) is not active without engine load.
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