AUDI A4 2000 B5 / 1.G AWM Engine Oxygen Sensor Control Checking Owner's Manual

- Replace Heated Oxygen Sensor (HO2S)-G39-.
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If specified value is obtained:

- Check voltage supply of oxygen sensor
heating.

Checking voltage supply for oxygen sensor
heating

Note:
When the Engine Control Module (ECM) switches oxygen sensor heating
on and off, it may be observed via the function "read measuring value
block", in display group number 041 display field 2.
If there is no voltage: - Connect multimeter between terminal 3 and 4 for voltage
measurement.
- Start engine.

Specification: approx. battery voltage

- Connect multimeter for voltage measurement as follows.Harness connector
Terminal
Measure to
3 (B+) Vehicle Ground (GND)
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- Operate starter briefly.


Specification: approx. battery voltage
If there is no voltage again:

- Check wire connection from terminal 3 of
connector to Fuel Pump (FP) relay via fuse for
open circuit:

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
If voltage supply is OK:

Note: - Connect multimeter for voltage measurement as follows:Harness connector
Terminal
Measure
to
4 (Ground -GND- activation of Engine Control Module -
ECM-) B+
- Start engine.

Specification: approx. battery voltage
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When the Engine Control Module (ECM) switches oxygen sensor heating
on and off, it may be observed via the function "read measuring value
block", in display group number 041 display field 2.
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- Switch ignition off.
If there is no voltage:

- Connect VAG1598/31 test box at wiring harness
to Engine Control Module (ECM), do not connect
ECM Page 24
-19
.

Electrical Wiring Diagrams, Troubleshooting & Component Locations
If wire connection is OK, but there is no Ground (GND) supply for oxygen
sensor heating: - Check the following wire connection for open circuit:Harness connector
Terminal
VAG1598/31 test box
Socket
4 5
- Repair open circuit if necessary.- Replace Engine Control Module (ECM) Page 24
-22
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Heated Oxygen Sensor (HO2S) and
oxygen sensor control after Three Way
Catalytic Converter (TWC), checking


Note:
The oxygen sensor before catalytic converter
(bank 1, sensor 1) regulates to Lambda 1. If this
oxygen sensor is damaged, e.g. due to soiling or
overheating, the regulation value may have
shifted. Deviations from Lambda 1 are detected
by the oxygen sensor after catalytic converter
(bank 1, sensor 2). If it recognizes the deviations
downward or upward, it influences the regulation
before catalytic converter, generally increasing or
decreasing it respectively.
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Special Tools and Equipment

VAG1526A
VAG1594A
VAG1598/31
VAG1788/10 RPM adjuster
VAS5051 with VAG5051/1
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Test requirements:

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

Test sequence

- Connect VAS5051 tester Page 01
-7 and
select vehicle system "01 - Engine electronics".
Engine must run at idle for this.

- Install VAG1788/10 RPM adjuster on the
accelerator pedal and raise the engine speed to
2600 RPM.

Test requirement:

Engine running at 2600 RPM.

Display on VAS5051:
- In selection -1-, click on the diagnostic function "04 - Basic setting".
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Display on VAS5051:
1 - Enter display group Max. input value = 255
- Select function "030" in button field -2- for "display group number 030"
and press Q button to confirm input.

Display on VAS5051:
Note:
"Oxygen sensor status" indicates status of oxygen sensor control and
oxygen sensors. - Check specified value in display field -2-.
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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
-107

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
Notes:

The first position of the 3 digit indication (heating) fluctuates between 0 and 1.
Oxygen sensor control of oxygen sensor after catalytic converter (B1-S2) is not active without engine load.
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