AUDI A3 1998 8L / 1.G ATW Engine Oxygen Sensor Control User Guide

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If specified value is not obtained:
If specified value is obtained:
Checking oxygen sensor wires - 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 Heated Oxygen Sensor (HO2S) -G39-.

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.
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- Connect VAG1598/31 test box at wiring harness
to Engine Control Module (ECM), do not connect
ECM Page 24
-19
.

If wire connection is OK: - Check following wire connections for open circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
3 51
4 70
- Repair open circuit if necessary.
- Check wires to each other for short circuit.
- Replace Engine Control Module (ECM) Page 24
-23
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Oxygen sensor aging (oxygen sensor
before catalytic converter), checking


Special tools and equipment

VAG1788/10 RPM adjuster

or
Test requirement:
VAS5051 with VAG5051/1VAG1551 with VAG1551/3ACoolant Temperature at least 80 C.
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Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select control module for engine electronics
using "address word" 01 Page 01
-10
. Engine
must run at idle.
Rapid data transfer
HELP
Select function XX

When indicated on display
- Press buttons -0- and -4- to select "Initiate basic setting" and press -Q-
button to confirm input.
Basic Settin
g
Q
Enter displa
y group number XXX

When indicated on display
- Press buttons -0-, -3- and -4- to select "display group number 034" and
press -Q- button to confirm input.
System in basic setting 34
1
2
3
4

When indicated on display
Note:
This process can take a few minutes. - Use VAG1788/10 RPM adjuster to adjust engine speed to between
1800 and 2200 RPM.
- Check specified value in display field 4:
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Display fields

1 2 3 4
Display group 034: Diagnostic oxygen sensor aging
Display xxxx/min
xxx C
x.x s
---
Indicated Engine speed
(RPM) Exhaust
temperature Period duration Oxygen sensor before
Catalytic converter Diagnostic
condition
Functional
range

Test OFF
Test ON
B1-S2 OK
B1-S2 not OK
Specified
value 1800 to 2200
RPM more than 350 C
0.0 to 1.0 s B1-S2 OK
Note


If specified value is not obtained Continuation, Page 24
-
86

Note for display field 2:
Calculated value from engine speed and engine load.
Note for display fields 3 and 4:
Period duration is the time between two oxygen sensor voltage jumps (e.g. rich - lean - rich) and is therefore a measurement
of the aging condition of the oxygen sensor. If the specified time is exceeded, display field 4 will indicate = B1-S1 not OK.
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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-.
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Heated Oxygen Sensor (HO2S) and
oxygen sensor control after Three Way
Catalytic Converter (TWC), checking


Note:
Oxygen sensor control behind catalytic converter
is superior to oxygen sensor control before
catalytic converter and is responsible for control
correction.

It corrects slight changes in the mixture (i.e. enrichment) via the oxygen
sensor before catalytic converter by holding oxygen sensor control before
catalytic converter at its higher or lower point for a specific time (dwell
time). If this time is in the positive range (i.e. 50 ms), mixture is shifted in
the -enrich- direction. If it is in the negative range (e.g. -50 ms), mixture
will be shifted in the -lean- direction.
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Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
VAG1788/10 RPM adjuster
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3A
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Test requirements:

Road test performed and DTC memory
erased.
Coolant Temperature at least 80 C.

Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select control module for engine electronics
using "address word" 01 Page 01
-10
. Engine
must run at idle.
Rapid data transfer
HELP
Select function XX

When indicated on display
Note:
During basic setting, the Evaporative Emission (EVAP) canister purge
regulator valve (EVAP valve -N80-) is closed and the A/C compressor is
switched off - Press buttons -0- and -4- to select "Initiate basic setting" and press -Q-
button to confirm input.
Basic Settin
g
Q
Enter displa
y group number XXX

When indicated on display
- Press buttons -0-, -3- and -4- to select "display group number 034" and
press -Q- button to confirm input.
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System in basic setting 34
1
2
3
4

When indicated on display
Note:
This process can take a few minutes. - Use VAG1788/10 RPM adjuster to adjust engine speed to between
2800 and 3200 RPM.
- Continue test as soon as display field 2 indicates an exhaust
temperature of more than 350 C. - Press -C- button.
- Use VAG1788/10 RPM adjuster to adjust engine speed to between
1800 and 2200 RPM.
Basic Setting
Q
Enter displa
y group number XXX

When indicated on display
- Press buttons -0-, -3- and -0- to select "display group number 030" and
press -Q- button to confirm input.
System in basic setting 30
1
2
3
4

When indicated on display
Note:
"Oxygen sensor status" indicates status of oxygen sensor control and
oxygen sensor. - Check oxygen sensor status for oxygen sensor behind catalytic
converter in display field 2.
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