lock AUDI A6 1995 C5 / 2.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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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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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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Read Measurin
g Value Block
Q
Input display group number XXX

When indicated on display:
- Press buttons -0-, -4- and -2- to select "display group number 042" and press -Q-
button to confirm input.
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Read Measuring Value Block 42
1
2
3
4

When indicated on display:
- Check specified values in display fields 1 and 3.

Display fields

1 2 3 4
Display group 042: Oxygen sensor heating (bank 2) at idle
Display
xxx kOhm ---
xxx kOhm ---
Indicated
Bank 2, sensor 1 Condition of heating
Bank 2, sensor 2 Condition of heating
Functional range Htng. bef. cat. ON
Htng. bef. cat. OFF Htng. beh. cat. ON
Htng. beh. cat. OFF
Specified value
0 to 0.9 kOhm Htng. bef. cat. ON/OFF
0 to 0.9 kOhm Htng. beh. cat. ON/OFF Important notes to display fields 1, 2, 3 and 4:

If oxygen sensors have not yet reached their operating temperature, there will be no indication in display fields 1 and 3,
i.e. they will both be empty. (increase engine speed to obtain specified values).
After reaching operating temperature of the two oxygen sensors, a resistance of less than 0.9 kOhm must be indicated in
display fields 1 and 3.
Do not continue test until a resistance of less than 0.9 kOhm is indicated in display fields 1 and 3.
At certain points of operation, the ECM "pulses" oxygen sensor heating. This means that oxygen sensor heating is
switched on and off at these points. It is entirely possible that the specified value "Htng. bef. Cat. OFF" or "Htng. beh. Cat.
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- Start engine.


Specification: approx. battery voltage,
possibly fluctuating

Notes:

At certain operating points, the ECM "pulses"
the Ground (GND) for oxygen sensor heating.
This means that the Ground (GND) is
constantly switched on and off at these points.
It is therefore possible that the voltage
displayed on the tester will fluctuate.
It is possible to observe the ECM switching
oxygen sensor heating on and off within the
function "read measuring value block", display
group numbers 041 and 042.
If there is no voltage:

- Connect multimeter for voltage measurement as follows:Harness connector
Terminal
Measure to
1 (B+) Vehicle Ground (GND)
- Operate starter briefly.
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Oxygen sensor, removing and installing


Special tools and equipment

Removing
Component location of harness connectors Overview of component
locations, page Page 24
-5
3337 wrench, 7-piece set Locking compound G 052 112 A3
- Disconnect 4-pin harness connector leading to respective oxygen
sensor.
- Open cable ties.
- Unscrew oxygen sensor using special tool 3337.
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