engine AUDI A8 1999 D2 / 1.G ATQ Engine Oxygen Sensor Control Checking

24-117

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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Display fields

1 2 3 4
Display group 041: Oxygen sensor heating (bank 1) at idle
Display
xxx kOhm ---
xxx kOhm ---
Indicated
Bank 1, sensor 1 Condition of heating
Bank 2, sensor 1 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.
OFF" will appear in display fields 2 and 4

- Press -C- button.
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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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24-123
If there is no voltage again:

- Check wire connection from terminal 1 to Fuel
Pump (FP) relay via fuse for open circuit.

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

If there is no voltage: - Connect multimeter for voltage measurement as follows:Harness connector
Terminal
Measure
to
2 (Ground -GND- activation of Engine Control Module -
ECM-) B+
- Start engine.

Specification: approx. battery voltage, possibly fluctuating
- Switch ignition off.
- Connect VAG1598/31 test box at wiring harness to ECM, do not
connect ECM Page 24
-17
.
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pair&id=AUDI.B5.FU05.24.3