coolant AUDI A4 1998 B5 / 1.G ATQ Engine Oxygen Sensor Control Checking

24-79

Notes:

For the defined troubleshooting procedure, it is
possible, to switch oxygen sensor control off by
selecting display group 099 under "basic
setting" and switch it on again under "read
measuring value block".
After selecting display group 099 (either in
"basic setting" or "read measuring value
block"), it is possible to switch back and forth
between "basic setting" (function 04) and "read
measuring value block" (function 08) by
pressing buttons 4 or 8 on the VAG1551.
Once function 04 "basic setting" is exited,
oxygen sensor control is automatically switched
on again.

Test requirements:
Road test performed and DTC memory
erased.
Coolant temperature at least 80 C
Display group 4, display field 3
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24-89

Checking primary voltage
Component location of harness connectors
Overview of component locations, page Page
24
-5

Note:
Coolant reservoir screws must be removed and
coolant reservoir must be placed to side in order
to access this harness connector. The coolant
hoses can remain connected.

Test requirement:

Fuse for oxygen sensor are OK

- Disconnect 4-pin harness connector leading to
respective oxygen sensor.

If specified value is not 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
-90
or Bank Pa
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24-93

Oxygen sensor aging (oxygen sensor
before catalytic converter), checking


Special Tools and Equipment

VAG1788/10 RPM adjuster

Test requirement:
VAS5051 with VAG5051/1
orVAG1551 with VAG1551/3BCoolant temperature at least 80 C Display group 4, display field 3
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24-98

Notes:

The oxygen sensor control behind catalytic
converter overrules the oxygen sensor control
before catalytic converter. It serves as a
corrective control.

Test requirements:
Test sequence
It corrects slight changes in the mixture (i.e. enrichment) via 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 it is in the negative
range (i.e.--50 ms), mixture is shifted in the -lean- direction. Road test performed and DTC memory erased. Coolant temperature at least 80 C Display group 4, display field 3
- Connect VAS5051 tester or VAG1551 scan tool and select the control
module for engine electronics using "address word" 01 Page 01
-9 .
Engine must run at idle for this.
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