1996 AUDI A4 catalytic converter

24-91


Display fields

1 2 3 4
Display group 030: Oxygen sensor status with engine at idle
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
-99

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:

Oxygen sensor control of oxygen sensor behind catalytic converter (B1-S2) is not active without engine load.
The first position of the 3 digit indication (heating) fluctuates between 0 and 1.
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Checking oxygen sensor control behind
catalytic converter

- Press -C- button.Basic Setting
Q
Enter 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 of oxygen sensor control before catalytic converter in
display field 3 and diagnostic result in display field 4.
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24-93


Display fields

1 2 3 4
Display group 037: Diagnostic oxygen sensor control system
Display xxx %
x.xxx volts
xxx ms
---
Indicated Engine
load Oxygen sensor voltage
Bank 2, sensor 1 Dwell time, oxygen sensor control
before catalytic converter, bank 1 Diagnostic condition
Functional
range


Test OFF
Test ON
System OK
System not OK
Specified
value 15 to 33
% 0.100 to 0.900 V
-150 to 150 ms System OK
Note

If specified value is not
obtained: Evaluation display
field 2 Page 24
-94

If value climbs to above 300 ms,
this indicates a leaking exhaust
system or faulty oxygen sensor If "SYST not OK" is
displayed: Check DTC
memory Page 01
-16

Note for display field 3:
Oxygen sensor control behind catalytic converter is superior to oxygen sensor control before catalytic converter and is
responsible for control correction. 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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24-94
Evaluation display group 037 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
-96


Open circuit in wire 3 between oxygen sensor
and control module
larger than
1.100 V Short circuit to B+ in wire 4 between oxygen
sensor and control module - Check oxygen sensor wiring, oxygen sensor
behind catalytic converter Page 24
-97

smaller than
0.150 V
Short circuit to Ground (GND) in wire 4 between
oxygen sensor and control module
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24-95

Continuation
If specified value in display field 3 and 4 is not
obtained:

- Road test vehicle in order to free oxygen sensor
of possible residue and repeat test.
If specified value in display field 3 and 4 is not
obtained, even after road test:

- Replace Heated Oxygen Sensor (HO2S) -
G39-.

Note:
If oxygen sensor voltage is OK and dwell time of
oxygen sensor control behind catalytic converter
is still above 1200 ms, even after a road test, this
suggests aging of the oxygen sensor before
catalytic converter.
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24-96

Checking primary voltage

Note:
Coolant reservoir screws must be removed and coolant reservoir must be
placed to side in order to access the harness connector. The coolant
hoses can remain connected. - Disconnect 4-pin harness connector -1- (brown) to Oxygen Sensor
(O2S) behind Three Way Catalytic Converter (TWC) -G130-.

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 wiring.
- Replace Oxygen Sensor (O2S) behind Three Way Catalytic Converter
(TWC) -G130-.
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24-97

Checking oxygen sensor wires

Note:
Coolant reservoir screws must be removed and coolant reservoir must be
placed to side in order to access the harness connector. The coolant
hoses can remain connected. - Disconnect 4-pin harness connector -1- (brown) to Oxygen Sensor
(O2S) behind Three Way Catalytic Converter (TWC) -G130-.
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.

- Check following wire connections for open circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
3 68
4 69
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24-99


Oxygen Sensor (O2S) heater -Z19- and
oxygen sensor heater 1 -Z29- for oxygen
sensor before catalytic converter and
oxygen sensor behind catalytic converter,
checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
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p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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pair&id=AUDI.B5.FU06.24.2