AUDI A4 1998 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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Test requirements:

Exhaust system free of leaks.
Coolant Temperature at least 80 C.

Test sequence

- Connect VAS5051 tester Page 01
-7 and
select vehicle system "01 - Engine electronics".
Engine must run at idle for this.

Display on VAS5051:
- In selection -1-, click on the diagnostic function "04 - Basic setting".
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Display on VAS5051:
1 - Enter display group Max. input value = 255
- Select function "030" in button field -2- for "display group number 030"
and press Q button to confirm input.

Display on VAS5051:
Notes: - Check specified value in display field -1-.
Increase engine speed to obtain specified values faster. "Oxygen sensor status" indicates status of oxygen sensor control and
oxygen sensors.
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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
-81

If specified value is obtained but there is a malfunction stored in DTC memory Check oxygen
sensor adaptation values and control, Page 24
-75

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
Note:
The first field of the 3 digit indication (heating) fluctuates between 0 and 1.
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Display on VAS5051:
Checking oxygen sensor adaptation values and control - Do not continue test until indication in display field -1- has
reached "111" at least once.
-
Press button 2 times to change into display group 032.- Check oxygen sensor adaptation values in display fields -1- and -
2-.

Display fields

1 2 3 4
Display group 036: Oxygen sensor adaptation values
Display
xx.x %
xx.x %


Indicated
Oxygen sensor adaptation value bank 1,
sensor 1at idle (additive) Oxygen sensor adaptation value bank 1, sensor
1at partial throttle(multiple)
Specified
value -6.0 to 6.0 %
-10.0 to 10.0 %


Note
If specified value is not obtained Page 24
-78



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-
Press button to change into display group
033.
- Check oxygen sensor control in display fields -1-
and -2-.

Display fields

1 2 3 4
Display group 033: Oxygen sensor control
Display
xx.x %
x.xxx V


Indicated
Oxygen sensor control bank 1, sensor 1
Oxygen sensor voltage, Bank 1, sensor 1

Specified
value Value must fluctuate at least 2 % in the
range -10.0 to 10.0 % 0.130 to 3.600 volts


Note
If specified value is not obtained
Continuation, Page 24
-77

If specified value is not obtained Evaluation
display group 033, Page 24
-80



Note for display field 2:
The oxygen sensor voltage signal which is processed and calendered by the Engine Control Module (ECM) will be displayed.
1.5 volts in display corresponds to Lambda 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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Display group 032 Display field: 1 / 2
Possible cause
Corrective action
Oxygen sensor adaptation
values below specified
range
Leak in intake area (pressure side between
turbocharger and intake manifold) - Check intake system for leaks and
repair false air Page 24
-68



Oil thinning- Oil change or perform swift country road
test

High oil consumption

Mass Air Flow (MAF) sensor faulty- Mass Air Flow (MAF) sensor, checking
Page 24
-59



Evaporative Emission (EVAP) canister purge
regulator valve remains stuck in open
position - Check Evaporative Emission (EVAP)
canister purge regulator valve Page
24
-114



Fuel pressure too high- Check fuel pressure regulator Page
24
-32



Fuel injector does not close- Check fuel injectors Page 24
-37
.


Oxygen sensor heating faulty
Oxygen sensor faulty- Check oxygen sensor heating Page
24
-89

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Display group 032 Display field: 1 / 2
Possible cause
Corrective action
Oxygen sensor adaptation
values via specified range
False air in intake area- Check intake system for leaks and repair
false air Page 24
-68


Fuel pressure too low- Check fuel pressure regulator Page 24
-32

Mass Air Flow (MAF) sensor faulty- Mass Air Flow (MAF) sensor, checking
Page 24
-59


Oxygen sensor heating faultyOxygen sensor faulty- Check oxygen sensor heating Page 24
-89

Fuel injector does not open or opens
only partially - Check fuel injectors Page 24
-37
.

Evaporative Emission (EVAP)
Canister Purge Regulator Valve sticks - Check Evaporative Emission (EVAP)
canister purge regulator valve Page 24
-114

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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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