AUDI A4 2000 B5 / 1.G ATW Engine Oxygen Sensor Control Workshop Manual

24-71


Oxygen sensor control,
checking Oxygen sensor and oxygen sensor control
before catalytic converter, checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3A
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Test requirements:

Exhaust system free of leaks.
Coolant Temperature at least 80 C.

Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select control module for engine electronics
using "address word" 01 Page 01
-10
. Engine
must run at idle.
Rapid data transfer
HELP
Select function XX

When indicated on display
- Press buttons -0- and -4- to select "Initiate basic setting" and press -Q-
button to confirm input.
Basic Settin
g
Q
Enter displa
y group number XXX

When indicated on display
Note: - Press buttons -0-, -3- and -0- to select "display group number 030" and
press -Q- button to confirm input.
- Check specified value in display field 1.
Increase engine speed to obtain specified values faster. "Oxygen sensor status" indicates status of oxygen sensor control and
oxygen sensors.
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Display fields

1 2 3 4
Display group 030: Oxygen sensor status
Display
X X X X X X

Indicated
Oxygen sensor status, bank 1, sensor 1 Oxygen sensor status, bank 2, sensor 1

Functional
range 0 = off
1 = on 0 = off
1 = on

Specified
value 1 1 1 1 1 0

Note
If specified value is not obtained Page 24
-80

If specified value is obtained but there is a malfunction stored in DTC memory Check oxygen
sensor adaptation values and control, Page 24
-74

Significance of 3 digit indications in display group 030 X
X
X
Display fields 1 and 2
X Oxygen sensor control: 0= not active; 1 = active
X Operational readiness of oxygen sensor: 0= not active; 1 = active
X Condition of oxygen sensor heater: 0= not active; 1 = active
Note:
The first field of the 3 digit indication (heating) fluctuates between 0 and 1.
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- Do not start test until indication in display field 1
has reached "111" at least once.

Checking oxygen sensor adaptation values
and control

- Press -C- button.Basic Settin
g
Q
Enter displa
y group number XXX

When indicated on display
- Press buttons -0-, -3- and -2- to select "display group number 032" and
press -Q- button to confirm input.
System in basic setting 32
1
2
3
4

When indicated on display
- Check oxygen sensor values in display fields 1 and 2:
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Display fields

1 2 3 4
Display group 036: Oxygen sensor adaptation values
Display
xx.x %
xx.x %


Indicated
Oxygen sensor adaptation value Bank 1,
sensor 1at idle (additive) Oxygen sensor adaptation value Bank 1, sensor
1at partial throttle(multiple)
Specified
value -10.0 to 10.0 %
can fluctuate slightly -10.0 to 10.0 %
can fluctuate slightly


Note
If specified value is not obtained Page 24
-78




- Press -C- button.Basic Settin
g
Q
Enter display group number XXX

When indicated on display
- Press buttons -0-, -3- and -3- to select "display group number 033" and
press -Q- button to confirm input.
System in basic setting 33
1
2
3
4

When indicated on display
- Check oxygen sensor control in display fields 1 and 2.
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Display fields

1 2 3 4
Display group 033: Oxygen sensor control
Display
xx.x %
x.xxx V


Indicated
Oxygen sensor control Bank 1, sensor 1
Oxygen sensor voltage, Bank 1, sensor 1

Specified
value Value must fluctuate at least 2 % in the
range -10.0 to 10.0 % Value must fluctuate approx. 0.3 V in the range
0.000 to 1.000 volts

Note
If specified value is not obtained
Continuation, Page 24
-77

If specified value is not obtained Evaluation
display group 033, Page 24
-80



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Continuation
If specified value in display field 1 is not obtained
or if value does not fluctuate at least 2 %:

- Road test vehicle in order to free oxygen sensor
of possible residue and repeat test.
If specified value in display field 1 is not obtained
even after road test or if value does not fluctuate
at least 2 %:

- Check primary voltage Page 24
-80
.

- Check oxygen sensor heating Page 24
-99
.

- Check oxygen sensor before catalytic converter
for aging Page 24
-83
.
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Display group 032 Display field: 1 / 2
Possible cause
Corrective action
Oxygen sensor adaptation
value in range: -10.0 to -25.0
%
Leak in intake area (pressure side between
turbocharger and intake manifold) - Check intake system for leaks and
repair false air Page 24
-68


Oil thinning- Oil change or perform swift country road
test
High oil consumption
Mass Air Flow (MAF) sensor faulty- Mass Air Flow (MAF) sensor, checking
Page 24
-60


Evaporative Emission (EVAP) canister
purge regulator valve remains stuck in open
position - Check Evaporative Emission (EVAP)
canister purge regulator valve Page
24
-107


Fuel pressure too high- Check fuel pressure regulator Page
24
-33


Fuel injector does not close- Check fuel injectors Page 24
-38
.

Oxygen sensor heating faultyOxygen sensor faulty- Check oxygen sensor heating Page
24
-99

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Display group 032 Display field: 1 / 2
Possible cause
Corrective action
Oxygen sensor adaptation
value in range:10.0 to 25.0 %
False air in intake area- Check intake system for leaks and repair
false air Page 24
-68


Fuel pressure too low- Check fuel pressure regulator Page 24
-
33


Mass Air Flow (MAF) sensor faulty- Mass Air Flow (MAF) sensor, checking
Page 24
-60


Oxygen sensor heating faultyOxygen sensor faulty- Check oxygen sensor heating Page 24
-
99


Fuel injector does not open or opens
only partially - Check fuel injectors Page 24
-38
.

Evaporative Emission (EVAP)
Canister Purge Regulator Valve sticks - Check Evaporative Emission (EVAP)
canister purge regulator valve Page 24
-
107

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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.
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