AUDI A4 1995 B5 / 1.G AFC Engine Heated Oxygen Sensor Before Converter Checking Workshop Manual

24-49


Heated Oxygen Sensor
(HO2S) before Three Way
Catalytic Converter (TWC),
checking

Heated oxygen sensor, checking

Notes:

G39 = Heated Oxygen Sensor (HO2S), bank
1
G108 = Heated Oxygen Sensor (HO2S) 2, bank
2
Functional check of HO2S -G39- or -G108-
Repair Group 01, Read measuring value block,
display group 010 or 041

- Disconnect Heated Oxygen Sensors (HO2S) -
G39- or -G108- harness connector (component
locations page 24
-1 ).

If continuity is not obtained: -
Switch multimeter (Fluke 83 or equivalent) to measure resistance ( )
and check for continuity between terminal 4 oxygen sensor signal wire
(measured at oxygen sensor connector) and engine Ground (GND).
Pa
ge 1 of 7 Heated Ox
yg
en Sensor
(HO2S
) before Three Wa
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ytic Converter
(TWC
), checkin
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pair&id=AUDI.B5.FU01.24.12

If continuity obtained: - Replace heated oxygen sensor.

- Switch multimeter to 2 volt range and connect between terminal 4 on
harness connector and engine Ground (GND).
Pa
ge 2 of 7 Heated Ox
yg
en Sensor
(HO2S
) before Three Wa
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ytic Converter
(TWC
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24-50

- Switch ignition ON.


Specified value: 400 50 mV If the specified value is not obtained, check
wiring to ECM as follows:

- Switch ignition OFF.

- Connect VAG 1598/19 test box to ECM harness
connector page 01
-255
.

- Check wiring for continuity between terminal 4
(HO2S -G39-) and terminal 20 on ECM
connector A.


Specified value: max. 1
- Check wiring for continuity between terminal 4
(HO2S 2 -G108-) and terminal 21 on ECM
connector A.


Specified value: max. 1 If the specified value is not obtained:

- Eliminate short or open circuit in wiring using wiring diagram.
Pa
ge 3 of 7 Heated Ox
yg
en Sensor
(HO2S
) before Three Wa
y Catal
ytic Converter
(TWC
), checkin
g
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play?action=Goto&t
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pair&id=AUDI.B5.FU01.24.12

If wiring OK:
- Replace ECM page 01
-265
.
Pa
ge 4 of 7 Heated Ox
yg
en Sensor
(HO2S
) before Three Wa
y Catal
ytic Converter
(TWC
), checkin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
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pair&id=AUDI.B5.FU01.24.12

24-51

Oxygen sensor heater, checking

Notes:

Z19 = Oxygen Sensor (O2S) heater, bank 1
Z28 = Oxygen Sensor (O2S) heater, bank 2
For functional check of O2S heaters -Z19- or -
Z28- Repair Group 01, Read measuring
value block, display group 040

- Disconnect O2S heater connector -Z19- or -Z28-
(component locations page 24
-1 ).

If the specified value is not obtained: - Switch multimeter (Fluke 83 or equivalent) to measure voltage and
connect between terminals 1 (B+) and 2 (GND).
- Start engine and let idle.
Specified value: approx. 12 to 14 volts
- Check oxygen sensor heater fuse.
- Check fuel pump relay page 24
-24
.

- Check wiring for continuity between terminal 1 and fuse in fuse holder
using wiring diagram (if necessary check terminal assignments).
Pa
ge 5 of 7 Heated Ox
yg
en Sensor
(HO2S
) before Three Wa
y Catal
ytic Converter
(TWC
), checkin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.24.12

Specified value: max. 1
Pa
ge 6 of 7 Heated Ox
yg
en Sensor
(HO2S
) before Three Wa
y Catal
ytic Converter
(TWC
), checkin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.24.12

24-52

- Check wiring for continuity between terminal 2
(O2S heater -Z19-) and terminal 10 on ECM
connector E.


Specified value: max. 1
- Check wiring for continuity between terminal 2
(O2S heater -Z28-) and terminal 9 on ECM
connector E.


Specified value: max. 1 If the specified value is obtained:

Note:
With small increases in temperature, resistance will increase sharply.
If the specified value is not obtained: -
Switch multimeter (Fluke 83 or equivalent) to measure resistance ( )
and connect between between terminals 1 and 2.
Specified value at room temperature: approx. 2 to 5 - Replace heated oxygen sensor.
Pa
ge 7 of 7 Heated Ox
yg
en Sensor
(HO2S
) before Three Wa
y Catal
ytic Converter
(TWC
), checkin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.24.12