catalytic converter AUDI A4 1999 B5 / 1.G ATQ Engine Oxygen Sensor Control Checking

24-100

- Press -C- button.

- Let engine continue to idle Basic Setting
Q
Input 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 sensors. - Check oxygen sensor status for oxygen sensor behind catalytic
converter in display fields 2 and 4.
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Display fields

1 2 3 4
Display group 030: Oxygen sensor status with engine at idle
Display X X X
X X X X X X
X X X
Indicated Oxygen sensor status, bank 1,
sensor 1 Oxygen sensor
status
Bank 2, sensor 1 Oxygen sensor status, bank 2,
sensor 1 Oxygen sensor
status
Bank 2, sensor 2
Functional
range 0 = off
1 = on 0 = off
1 = on 0 = off
1 = on 0 = off
1 = on
Specified
value 1 1 1
1 1 0 1 1 1
1 1 0
Notes
Meaning of display Page 24
-102

If specified value is not obtained Page 24
-111

If specified value is obtained but there is a malfunction stored in DTC memory Check oxygen
sensor control, page Page 24
-105

Notes:

Oxygen sensor control of oxygen sensor behind catalytic converter (bank 1 sensor 2 and bank 2 sensor 2) are not active
without engine load, meaning that the display is 0.
The first position of the 3 digit indication (heating) fluctuates between 0 and 1.
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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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24-105

Checking oxygen sensor control behind
catalytic converter

- Perform a test drive of approx. 10 minutes.

WARNING!

Observe safety precautions to reduce the risk
of accidents during road test Page 24
-1 .

- Let engine continue to run at idle.Basic Setting
Q
Input displa
y group number XXX

When indicated on display:
- Press buttons -0-, -3- and -7- to select "display group number 037" and
press -Q- button to confirm input.
System in Basic Setting 37
1
2
3
4

When indicated on display:
- Check oxygen sensor voltage in display field 2.
- Check dwell time between oxygen sensor 1 before catalytic converter
and oxygen sensor 2 behind catalytic converter in display field 3 and
diagnostic result in display field 4.
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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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24-109
Evaluation of display group 037 and 038 Display field: 2
Possible cause
Corrective action
constant
about 0.450 V
Open circuit in wire 4 between oxygen sensor
and control module - Check primary voltage Page 24
-111


Open circuit in wire 3 between oxygen sensor
and control module
larger than
1.000 V Short circuit to B+ in wire 4 between oxygen
sensor and control module - Check oxygen sensor wiring and oxygen sensor
behind catalytic converter Page 24
-112

smaller than
0.150 V
Short circuit to Ground (GND) in wire 4 between
oxygen sensor and control module
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24-110

If specified value in display group 037 and
038 display field 3 or 4 is not obtained:

- Search for leaking air at exhaust system or
catalytic converter (check screw clamps and
exhaust system for damage).

- Check if possibly the oxygen sensors behind
catalytic converter of cylinder bank 1 and 2 have
been switched, in case of extremely different
values (e.g. +500 ms, - 500 ms) of display fields
3 (oxygen sensor correction value) in the
measuring value blocks 037 and 038.
If none of the listed causes applies:

- Replace respective oxygen sensor -before-
catalytic converter
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24-111

Checking primary voltage
Component location of harness connectors
Overview of component locations - page Page
24
-5

- Disconnect 4-pin harness connector leading to
respective oxygen sensor.

If specified value is not obtained:
If specified value is obtained: - 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 wires Bank 1 page Page 24
-112
or bank 2
page Page 24
-114
.
- Replace appropriate oxygen sensor behind catalytic converter.
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