ESP AUDI TT 1995 8N / 1.G ATW Engine Oxygen Sensor Control Workshop Manual

24-87

Heated Oxygen Sensor (HO2S) and
oxygen sensor control after Three Way
Catalytic Converter (TWC), checking


Note:
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. 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 (e.g. -50 ms), mixture
will be shifted in the -lean- direction.
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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.
Pa
ge 23 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