air condition AUDI A6 1995 C5 / 2.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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Significance of 3 digit indication of display group 030 X
X
X
Display fields 1 to 4
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 heating
0= not active
1 = active
Notes:

The oxygen sensor control of the oxygen sensors behind catalytic converter (B1-S2 and B2-S2) are not active at certain
operation points without engine load, that means that the third position of the oxygen sensor controls behind catalytic
converter can fluctuate between 0 and 1.
The first position of the 3 digit indication (heating) fluctuates between 0 and 1 at certain operation points.
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Display fields

1 2 3 4
Display group 034: Oxygen sensor aging diagnostic, oxygen sensor before catalytic converter (bank 1)
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 630 to 6800
70 to 850 C
0 to 3.0 s
Test OFF
Test ON
B1-S2 OK
B1-S2 not OK
Specified
value 1000 to 2400
RPM above 380 C 0.1 to 1.8 s B1-S2 OK
Notes


If the specified value is not reached, replace oxygen sensor 1
before catalytic converter (bank 1)
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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24-96

- Press buttons -0-, -3- and -5- to select "display
group number 035" and press -Q- button to
confirm input. System in Basic Setting 35
1
2
3
4

When indicated on display:
Note:
The test in display group 035 is activated simultaneously with the test in
display group 034 Therefore the test result is indicated immediately after
display group 035 is selected. - Check specified value in display field 4.

Display fields

1 2 3 4
Display group 035: Oxygen sensor aging diagnostic, oxygen sensor before catalytic converter (bank 2)
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 630 to 6800
70 to 850 C
0 to 3.0 s
B1-S2 OK
B1-S2 not OK
Specified
value 1000 to 2400
RPM above 380 C 0.1 to 1.8 s B1-S2 OK
Notes


If the specified value is not reached, replace oxygen sensor 2
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Significance of 3 digit indication of display group 030 X
X
X
Display fields 1 to 4
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 heating
0= not active
1 = active

- Press -C- button.Basic Setting
Q
Input displa
y group number XXX

When indicated on display:
- Press buttons -0-, -4- and -3- to select "display group number 043" and press -Q-
button to confirm input.
System in Basic Setting 43
1
2
3
4

When indicated on display:
- Check specified value in display field 4 after indication "Test ON" appears:
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Display fields

1 2 3 4
Display group 043: Oxygen sensor aging, oxygen sensor behind catalytic converter (bank 1)
Display xxxx/min
xxx C
x.xxx V
---
Indicated Engine speed
(RPM) Exhaust
temperature Voltage of oxygen sensor
behind catalytic converter,
bank 1 Diagnostic condition
Functional
range 630 to 6800
RPM 70 to 850 C
0.100 to 1.000 volts Test OFF
Test ON
B1-S2 OK
B1-S2 not OK
Specified
value 1800 to 2400
RPM above 380 C 0.100 to 1.000 volts B1-S2 OK
Notes



If specified value is not obtained
Check oxygen sensor heater Page
24
-116

If specified value B1-S2 OK" is obtained:

- Press -C- button.

- Press buttons -0-, -4- and -4- to select "display
group number 044" and press -Q- button to
confirm input.
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Display fields

1 2 3 4
Display group 044: Oxygen sensor aging, oxygen sensor behind catalytic converter (bank 2)
Display xxxx/min
xxx C
x.xxx V
---
Indicated Engine speed
(RPM) Exhaust
temperature Voltage of oxygen sensor
behind catalytic converter,
bank 2 Diagnostic condition
Functional
range 670 to 6800
RPM 70 to 850 C
0.100 to 1.000 volts Test OFF
Test ON
B2-S2 OK
B2-S2 not OK
Specified
value 1800 to 2400
RPM above 380 C 0.100 to 1.000 volts B2-S2 OK
Notes



If specified value is not obtained
Check oxygen sensor heater Page
24
-116

If specified value B2-S2 OK" is obtained:

- Press -C- button.
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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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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.
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Display fields

1 2 3 4
Display group 041: Oxygen sensor heating (bank 1) at idle
Display
xxx kOhm ---
xxx kOhm ---
Indicated
Bank 1, sensor 1 Condition of heating
Bank 2, sensor 1 Condition of heating
Functional range Htng. bef. cat. ON
Htng. bef. cat. OFF Htng. beh. cat. ON
Htng. beh. cat. OFF
Specified value
0 to 0.9 kOhm Htng. bef. cat. ON/OFF
0 to 0.9 kOhm Htng. beh. cat. ON/OFF Important notes to display fields 1, 2, 3 and 4:

If oxygen sensors have not yet reached their operating temperature, there will be no indication in display fields 1 and 3,
i.e. they will both be empty. (increase engine speed to obtain specified values).
After reaching operating temperature of the two oxygen sensors, a resistance of less than 0.9 kOhm must be indicated in
display fields 1 and 3.
Do not continue test until a resistance of less than 0.9 kOhm is indicated in display fields 1 and 3.
At certain points of operation, the ECM "pulses" oxygen sensor heating. This means that oxygen sensor heating is
switched on and off at these points. It is entirely possible that the specified value "Htng. bef. Cat. OFF" or "Htng. beh. Cat.
OFF" will appear in display fields 2 and 4

- Press -C- button.
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