2000 AUDI A8 catalytic converter

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.
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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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24-112

Testing Oxygen Sensor Wires
Component location of harness connectors
Overview of component locations, page Page
24
-5

- Disconnect green 4-pin harness connector 1 to
Oxygen Sensor (O2S) Behind Three Way
Catalytic Converter (TWC) -G130-.

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

- Check the following wire connections for open circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
3 68
4 69
- Repair open circuit if necessary.
- Check wires to each other for short circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
4 68
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24-114

Check oxygen sensor wires for Oxygen
Sensor (O2S) 2 Behind Three Way Catalytic
Converter (TWC) -G131-.
Component location of harness connectors
Overview of component locations, page Page
24
-5

- Disconnect brown 4-pin harness connector 2 to
Oxygen Sensor (O2S) 2 Behind Three Way
Catalytic Converter (TWC) -G131-.

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

- Check the following wire connections for open circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
3 10
4 11
- Repair open circuit if necessary.
- Check wires to each other for short circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
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24-116


Oxygen sensor heating for oxygen
sensors before and behind catalytic
converter, checking

Special Tools and Equipment

VAG1526A
VAG1594A
VAG1598/31
VAG1788/10 RPM adjuster
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3B
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- Check the following wire connection for open circuit:
Oxygen Sensor (O2S) heater -Z19- bank 1 before catalytic converter:
Harness connector
Terminal
VAG1598/31 test box
Socket
2 5
Oxygen Sensor (O2S) heater -Z28- bank 2 before catalytic converter:
Harness connector
Terminal
VAG1598/31 test box
Socket
2 4
Oxygen Sensor (O2S) heater -Z29- bank 1 behind catalytic converter:
Harness connector
Terminal
VAG1598/31 test box
Socket
2 63
Oxygen Sensor (O2S) heater -Z30- bank 2 behind catalytic converter:
Harness connector
Terminal
VAG1598/31 test box
Socket
2 6
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11/23/2002 htt
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play?action=Goto&t
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pair&id=AUDI.B5.FU05.24.3