AUDI A6 1999 C5 / 2.G ATQ Engine Oxygen Sensor Control Checking

24-109
Evaluation of display group 037 and 038 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
-111


Open circuit in wire 3 between oxygen sensor
and control module
larger than
1.000 V Short circuit to B+ in wire 4 between oxygen
sensor and control module - Check oxygen sensor wiring and oxygen sensor
behind catalytic converter Page 24
-112

smaller than
0.150 V
Short circuit to Ground (GND) in wire 4 between
oxygen sensor and control module
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If specified value in display group 037 and
038 display field 3 or 4 is not obtained:

- Search for leaking air at exhaust system or
catalytic converter (check screw clamps and
exhaust system for damage).

- Check if possibly the oxygen sensors behind
catalytic converter of cylinder bank 1 and 2 have
been switched, in case of extremely different
values (e.g. +500 ms, - 500 ms) of display fields
3 (oxygen sensor correction value) in the
measuring value blocks 037 and 038.
If none of the listed causes applies:

- Replace respective oxygen sensor -before-
catalytic converter
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Checking primary voltage
Component location of harness connectors
Overview of component locations - page Page
24
-5

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

If specified value is not obtained:
If specified value is 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
-112
or bank 2
page Page 24
-114
.
- Replace appropriate oxygen sensor behind catalytic converter.
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Testing Oxygen Sensor Wires
Component location of harness connectors
Overview of component locations, page Page
24
-5

- Disconnect green 4-pin harness connector 1 to
Oxygen Sensor (O2S) Behind Three Way
Catalytic Converter (TWC) -G130-.

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

- Check the following wire connections for open circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
3 68
4 69
- Repair open circuit if necessary.
- Check wires to each other for short circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
4 68
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If no malfunctions are found in wires: - Check shielded wire for short circuit to sensor wires.Harness connector
Terminal
VAG1598/31 test box
Socket
3 32
4 32
- Replace Engine Control Module (ECM) Page 24
-21
.
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Check oxygen sensor wires for Oxygen
Sensor (O2S) 2 Behind Three Way Catalytic
Converter (TWC) -G131-.
Component location of harness connectors
Overview of component locations, page Page
24
-5

- Disconnect brown 4-pin harness connector 2 to
Oxygen Sensor (O2S) 2 Behind Three Way
Catalytic Converter (TWC) -G131-.

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

- Check the following wire connections for open circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
3 10
4 11
- Repair open circuit if necessary.
- Check wires to each other for short circuit.Harness connector
Terminal
VAG1598/31 test box
Socket
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4 10
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If no malfunctions are found in wires: - Check shielded wire for short circuit to sensor wires.Harness connector
Terminal
VAG1598/31 test box
Socket
3 32
4 32
- Replace Engine Control Module (ECM) Page 24
-21
.
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Oxygen sensor heating for oxygen
sensors before and behind catalytic
converter, checking

Special Tools and Equipment

VAG1526A
VAG1594A
VAG1598/31
VAG1788/10 RPM adjuster
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3B
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Note:
The heating circuit of the oxygen sensor is
monitored by On Board Diagnostic (OBD),
Check DTC memory Page 01
-15
.

- 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.Rapid data transfer
HELP
Select function XX

When indicated on display:
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Read Measurin
g Value Block
Q
Input displa
y group number XXX

When indicated on display:
- Press buttons -0-, -4- and -1- to select "display group number 041" and
press -Q- button to confirm input.
Read Measuring Value Block 41
1
2
3
4

When indicated on display:
Note:
Increasing engine speed accelerates the obtaining of specified values. - Check specified values in display fields 1 and 3.
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