1997 AUDI A8 AEB Engine Motronic MFI And Ignition System

24-17

Heated Oxygen Sensor (HO2S) and
oxygen sensor control (before TWC),
checking


Notes:

Connector for Heated Oxygen Sensor (HO2S)
before Three Way Catalytic Converter (TWC):
4-pin, brown
Component location Page 24
-1

Required special tools and test equipment

VAG 1551 or VAG 1552 Scan Tool (ST) with
VAG 1551/3 adapter cable
VAG 1598/22 test box
Multimeter US 1119 (Fluke 83 or equivalent)
VW 1594 connector test kit
Wiring diagram

Test conditions

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Engine Coolant Temperature (ECT) at least
85 C (185 F)
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24-18

Checking

- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with engine
running at idle) Page 01
-7 .
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block"
function 08, and press -Q- button to confirm input.
Read Measurin
g Value Block
HELP
Input displa
y group number XXX

Indicated on display
- Press buttons -0-, -3- and -2- to input display group number 32, and
press -Q- button to confirm input.
Read Measuring Value Block 32 1 2 3 4

Indicated on display (1-4 = display fields)
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24-19

- Check oxygen sensor control learning values
(display fields 1 and 2):

Display fields

1 2 3 4
Display group 32: Oxygen sensor control learning values
Display xx.x % xx.x %
Indicates Oxygen sensor control learning value at idle
(additive)
(before TWC) Oxygen sensor control learning value at partial load
(multiplicative)
(before TWC)
Range -26.0 to 26.0 % -25.0 to 25.0 %
Specified
value -8.0 to 8.0 %
(can vary slightly) -8.0 to 8.0 %
(can vary slightly)
If not as specified Page 24
-22
, Evaluation of display group 32

If displayed values are OK (as specified):

- Press -C- button.

- Press buttons -0-, -3- and -3- to input display
group number 33, and press -Q- button to
confirm input. Read Measuring Value Block 33

Indicated on display (1-4 = display fields)
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1 2 3 4
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24-20

- Check oxygen sensor control (display fields 1
and 2):

Display fields

1 2 3 4
Display group 33: Oxygen sensor control
Display xx.x % x.xxx V
Indicates Oxygen sensor control
(before TWC) Oxygen sensor voltage
(before TWC)
Range -25.0 to 25.0 % 0.000-1.000 V
Specified
value Within the range from -10.0 to 10.0 %
the value must change by at least 2 % Within the range from 0.000 to 1.000 V the value must
fluctuate at least 30 times per minute, and change by at
least 0.3 volts

If not as specified Page 24
-21
,
Continuation
If not as specified Page 24
-23
, Evaluation of display
group 33

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24-21

Continuation
If the value in display field 1 is NOT OK, or if the
value does not fluctuate by at least 2 %:

- Road test to condition oxygen sensor (eliminate
possible contamination) and repeat test.
If the value in display field 1 is still NOT OK, or if
it still does not fluctuate by at least 2 %:

- Check Oxygen Sensor (O2S) heater Page 24
-
27
.
If the value in display field 1 remains constant:

- Check oxygen sensor voltage (display field 2).

-
Press button to advance program
sequence.
- Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
input.

- Switch ignition off.
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24-22
Evaluation of display group 32 Display group:
32


Display fields: 1
+ 2
Possible cause
Corrective action
O2S control
learning value:
-26.0 to -8.0 %
Engine oil dilution (when partial load learning value
is normal, display field 2)
- Change engine oil, or carry out extensive road
test and check again.


Fuel pressure too high- Check fuel pressure regulator Page 24
-93


Fuel injector leaking- Check fuel injectors Page 24
-87


Oxygen Sensor (O2S) heater malfunction- Check O2S heater Page 24
-27
O2S control
learning value:
8.0-26.0 %
Intake air leaks ("false air") or exhaust manifold
leaks (when partial load learning value is normal,
display field 2)
Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo
Engine Mechanical, Engine Code(s): AEB, ATW, Repair Group 26
- Check intake air system for leaks Page 24
-
97

- Check exhaust system for leaks:


Fuel pressure too low- Check fuel pressure regulator Page 24
-93


Oxygen Sensor (O2S) heater malfunction- Check O2S heater Page 24
-27
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(MFI
) and i
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11/19/2002 htt
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play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1