lock AUDI A4 2000 B5 / 1.G APB Engine Oxygen Sensor Control Checking Workshop Manual

24-80
If the voltage does not change or only changes
slowly the following malfunctions are possible:

Slits or holes in probe head are blocked.
Oxygen sensor has been subjected to
excessive thermal stress.
Contact resistance in signal wire or Ground
(GND) wire.
Oxygen sensor too cold; sensor heater not
working.
Oxygen sensor damaged by contact spray or
similar product. (The contact spray is drawn
through the fine cavities in the electrical wiring
as a result of thermal fluctuations and capillary
effect.)
Oxygen sensor damaged by silicone vapors.
(The engine draws in traces of any silicone-
based sealants that may have been used. The
silicone does not burn and damages the oxygen
sensor.)
Pa
ge 2 of 61 Ox
yg
en sensor control, 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.FU04.24.2

24-82

Notes:

For the defined troubleshooting procedure, it is
possible to switch off the oxygen sensor control
by selecting Display Group 99 in "Basic Setting"
mode and to switch it on again by selecting
Display Group 99 in "Read Measuring Value
Block" mode.
After selecting Display Group 99 (either in
"Basic Setting" mode or in "Read Measuring
Value Block" mode) it is possible to switch back
and forth between function 04 ("Basic Setting")
and function 08 "Read Measuring Value Block")
by pressing buttons 4 and 8 on VAG1551 scan
tool.
When exiting the "Basic Setting" mode (function
04) the oxygen sensor control is automatically
switched on again.

Test conditions
Perform road test and do not erase DTC
memory.
Coolant temperature at least 85 C (Display
group 004, display field 3)
Pa
ge 4 of 61 Ox
yg
en sensor control, 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.FU04.24.2

24-113

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

- Check exhaust system and catalytic converter
for leaks (check clamps and exhaust for
damage)

- If the difference of the values in measuring
blocks, display fields 3 (oxygen sensor
correction value) is to large (e.g.:+500 ms, -500
ms), it is possible that the oxygen sensor are
interchanged (mixed up).
If none of the causes are identified:

- Replace particular oxygen sensor "before"
catalytic converter.
Pa
ge 41 of 61 Ox
yg
en sensor control, 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.FU04.24.2

24-114

Oxygen sensor heater for oxygen
sensor, checking


Note:
The oxygen sensor heating circuit is monitored
by the On Board Diagnostic (OBD). Check DTC
memory Page 01-15
.

- Connect vehicle diagnostic, testing and
information system VAS5051 or VAG1551 scan
tool and select engine electronics control
module by entering address word "01" Page
01
-9 . When doing this the engine must be at
idle.
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select function "Read Measuring Value
Block" and confirm entry with -Q- button.
Read Measurin
g Value Block
Input display group number XXX

Indicated on display
- Press buttons -0-, -4- and -1- to select "display group number 041" and
confirm entry with -Q- button.
Read Measuring Value Block 41
1
2
3
4

Indicated on display
Pa
ge 42 of 61 Ox
yg
en sensor control, 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.FU04.24.2