1997 AUDI A4 ground

24-80
Evaluation display group 033 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
-80


Open circuit in wire 3 between oxygen sensor
and control module
constant about
0.200 V Oxygen sensor faulty- Replace oxygen sensor
larger than
1.100 V Short circuit to B+ in wire 4 between oxygen
sensor and control module - Check oxygen sensor wiring, oxygen sensor
before catalytic converter Page 24
-81

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

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 -2- (black) to Heated Oxygen Sensor
(HO2S) -G39- before catalytic converter.
Pa
ge 10 of 37 Ox
yg
en sensor control, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.24.2

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
Pa
ge 24 of 37 Ox
yg
en sensor control, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.24.2

24-101


Note:
At higher temperatures, resistance climbs sharply.
If specified value is not obtained:
If specified value is obtained:
Checking voltage supply for oxygen sensor heating - Connect multimeter between terminal 1 and 2 for resistance
measurement.

Specified value at room temperature: 1 to 5
- Replace Oxygen Sensor (O2S).
- Check voltage supply of oxygen sensor heating Page 24
-101
.

- Connect multimeter between terminal 1 (B+) and 2 (Ground -GND-) for
voltage measurement.
Pa
ge 31 of 37 Ox
yg
en sensor control, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.24.2

24-102

- Start engine.


Specification: approx. battery voltage,
possibly fluctuating

Note:

At certain operating points, the ECM "pulses"
the Ground (GND) for oxygen sensor heating.
This means that the Ground (GND) is
constantly switched on and off at these points.
It is therefore possible that the voltage
displayed on the tester will fluctuate.
When the ECM switches oxygen sensor heating
on and off can be observed, if necessary, via
the function "read measuring value block"
display group number 041.
If there is no voltage:

- Connect multimeter for voltage measurement as
follows:

Harness connector
Terminal
Measure to
1 (B+) Vehicle Ground (GND)
Pa
ge 32 of 37 Ox
yg
en sensor control, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.24.2

24-103
If there is no voltage again:

- Check wire connection from terminal 1 of
connector to Fuel Pump (FP) relay via fuse for
open circuit:

Electrical Wiring Diagrams, Troubleshooting &
Component Locations If voltage supply is OK:

If there is no voltage: - Connect multimeter for voltage measurement as follows:Harness connector
Terminal
Measure
to
2 (Ground -GND- activation of Engine Control Module -
ECM-) B+
- Start engine.

Specification: approx. battery voltage, possibly fluctuating
- Switch ignition off.
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.
Pa
ge 34 of 37 Ox
yg
en sensor control, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.24.2

24-104


Oxygen Sensor (O2S) heater -Z19- for oxygen sensor before catalytic
converter:
Oxygen sensor heater 1 -Z29- for oxygen sensor behind catalytic
converter:
If wire connection is OK, but there is no Ground (GND) supply for oxygen
sensor heating: - Check following wire connection for open circuit:Harness connector
Terminal
VAG1598/31 test box
Socket
2 5
Harness connector
Terminal
VAG1598/31 test box
Socket
2 63
- Repair open circuit if necessary.
- Replace Engine Control Module (ECM) Page 24
-23
Pa
ge 35 of 37 Ox
yg
en sensor control, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.24.2