light AUDI A4 1995 B5 / 1.G ATQ Engine Oxygen Sensor Control Checking

24-76


Oxygen sensor control,
checking

Oxygen sensor control, function


Notes:
The oxygen sensors compare the oxygen
content of the air with residual oxygen content in
exhaust and deliver a voltage signal to the
control module.
The voltage signal "mixture rich (too little residual
oxygen)" is approx. 0.7 to 1.0 V.
The voltage signal "mixture lean (a lot of residual
oxygen)" is approx. +0.0 to 0.3 V.
At the transition from "rich" to "lean" and vice-
versa ( = 1.0) voltage will jump from 0.7 to 1.0
V to 0.0 to +0.3 V (or viceversa).
Due to the steep voltage jump, oxygen sensor
control cannot maintain the ideal mixture of =
1.0 as constant. Oxygen sensor control
constantly fluctuates back and forth between the
conditions "slightly too lean" and "slightly too
rich".
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- Press -C- button.

- Press buttons -0-, -3- and -2- to select "display
group number 032" and press -Q- button to
confirm input. System in Basic Setting 32
1
2
3
4

When indicated on display:
- Check oxygen sensor control in display fields 1 to 4:

Display fields

1 2 3 4
Display group 032: Oxygen sensor adaptation values before catalytic converter
Display
xx.x %
xx.x %
xx.x %
xx.x %
Indicated
Oxygen sensor
adaptation value
Bank 1 at idle
(additive) Oxygen sensor adaptation
value bank 1 at partial
throttle
(multiple) Oxygen sensor
adaptation value
Bank 2 at idle
(additive) Oxygen sensor adaptation
value bank 2 at partial
throttle
(multiple)
Functional
range -25.0 to 25.0 %
-25.0 to 25.0 %
-25.0 to 25.0 %
-25.0 to 25.0 %

Specified
value -10.0 to 10.0 %
can fluctuate
slightly -10.0 to 10.0 %
can fluctuate slightly -10.0 to 10.0 %
can fluctuate
slightly -10.0 to 10.0 %
can fluctuate slightly
Notes
If specified value is not obtained Page 24
-87

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24-98

Notes:

The oxygen sensor control behind catalytic
converter overrules the oxygen sensor control
before catalytic converter. It serves as a
corrective control.

Test requirements:
Test sequence
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 (i.e.--50 ms), mixture is shifted in the -lean- direction. Road test performed and DTC memory erased. Coolant temperature at least 80 C Display group 4, display field 3
- Connect VAS5051 tester or VAG1551 scan tool and select the control
module for engine electronics using "address word" 01 Page 01
-9 .
Engine must run at idle for this.
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Display fields

1 2 3 4
Display group 037: Diagnostic, oxygen sensor control system (bank 1)
Display xxx % x.xxx volts
xxx ms
---
Indicated Engine
load Oxygen sensor voltage
behind catalytic
converter, bank 1 Oxygen sensor correction
value between oxygen sensor
1 and oxygen sensor 2, bank 1 Diagnostic condition
Functional
range 12.0 to
100.0 % 0.100 to 1.000 V
-800 to 800 ms
Test OFF
Test ON
System OK
System not OK
Specified
value 12.0 to
26.0 % 0.100 to 1.000 V
-800 to 800 ms System OK
Notes
If specified value is not
obtained: Evaluation
display field 2
Page 24
-109

If specified value is not
obtained Page 24
-110

If "System not OK" is displayed:
Check Diagnostic Trouble Code
(DTC) memory Page 01
-15

or continuation Page 24
-110

Note for display field 3:
The oxygen sensor control behind catalytic converter overrules the oxygen sensor control before catalytic converter. It
corrects slight changes in the mixture (i.e. toward rich or lean) due to 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 this time is in the negative range (i.e. -50 ms), mixture
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24-108


Display fields

1 2 3 4
Display group 038: Diagnostic of oxygen sensor control system (Bank 2)
Display xxx % x.xxx V xxx ms
---
Indicated Engine
load Oxygen sensor voltage
behind catalytic converter,
bank 2 Oxygen sensor correction
value between oxygen sensor
2 and oxygen sensor 2, bank
1 Diagnostic condition
Functional
range 12.0 to
100.0 % 0.100 to 1.000 V -800 to 800 ms
System OK
System not OK
Specified
value 12.0 to
26.0 % 0.100 to 1.000 V -800 to 800 ms System OK
Notes
If specified value is not
obtained: Evaluation
display field 2 Page 24
-
109

If specified value is not
obtained Page 24
-110

If "SYST not OK" is displayed:
Check Diagnostic Trouble Code
(DTC) memory Page 01
-15

or continuation
Page 24
-110

Note for display field 3:
The oxygen sensor control behind catalytic converter overrules the oxygen sensor control before catalytic converter. It
corrects slight changes in the mixture (i.e. toward rich or lean) due to 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 this time is in the negative range (i.e. -50 ms), mixture
is shifted in the -lean- direction.
Pa
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p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.3