1999 AUDI A8 heater

24-27
Evaluation of display group 32 Display group:
32


Display fields:
1-4
Possible malfunction cause
Corrective action
O2S control
learning value:
-25.0 to -10.0
%
Engine oil dilution (when part load learning value is
normal display fields 2 and 4)
- Change engine oil, or carry out extensive
road test and check again


Fuel pressure too high- Check fuel pressure regulator page 24
-
111



Fuel injector leaking- Check fuel injectors page 24
-102


Oxygen Sensor (O2S) heater malfunction- Check O2S heater page 24
-34
O2S control
learning value:
10.0 to 25.0 %
Intake air leaks ("false air") or exhaust manifold leaks
(when partial load learning value is normal display
fields 2 and 4)
- Check intake air system for leaks page 24
-126

- Check exhaust system for leaks Repair
Manual, 2.8 Liter V6 5V General, Engine,
Repair Group 26


Fuel pressure too low- Check fuel pressure regulator page 24
-
111



Oxygen Sensor (O2S) heater malfunction- Check O2S heater page 24
-34
Pa
ge 36 of 166 Motronic Multi
port Fuel In
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) and i
gnition s
ystem
11/23/2002 htt
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yp
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24-34

Oxygen Sensor (O2S) heater before
TWC, checking


Notes:

Connector for Oxygen Sensor (O2S) heater -
Z19- (bank 1, sensor 1): 4-pin, black.
Connector for Oxygen Sensor (O2S) 2 heater -
Z28- (Bank 2, sensor 1): 4-pin, black.
Component locations page 24
-1 .

Required special tools and test equipment

VAG1551 or VAG1552 Scan Tool (ST) with
VAG1551/3 adapter cable
VAG1598/22 test box
Multimeter US1119 (Fluke 83 or equivalent)
VW1594 connector test kit
Wiring diagram

Test requirements
Pa
ge 44 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
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Fuse for Oxygen Sensor (O2S) heater(s) OK
Engine Coolant Temperature (ECT) at least
80 C (176 F)
Pa
ge 45 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
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pair&id=AUDI.B5.FU03.24.1

24-36

- Compare display and specified values (display
fields 1 and 2):

Display fields

1 2 3 4
Display group 40: Oxygen Sensor (O2S) heating (before and after TWC)
Display
xx.x
Htg.bC.ON/Htg.bC.OFF
xx.x
Htg.aC.ON/Htg.aC.OFF
Indicates Resistance of O2S heater
(before TWC)
(B1-S1 and B2-S1) O2S heater ON
or
O2S heater OFF
(before TWC)
(B1-S1 and B2-S1) Resistance of O2S heater
(after TWC)
(B1-S2 and B2-S2) O2S heater ON
or
O2S heater OFF
(after TWC)
(B1-S2 and B2-S2)
Range
0.0 - 65.0
--- --- ---
Specified value
2.4 - 9.2
Htg.bC.ON --- ---

If not as specified page 24
-37
, Continuation
--- ---
If displayed values are OK (as specified):

-
Press button.
-
Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
Pa
ge 47 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

24-45

Continuation

- Road test to condition oxygen sensor (eliminate
possible contamination) and repeat test.
If the values are still NOT OK:

- Check Oxygen Sensor (O2S) heater(s) page
24
-52
.

- Briefly accelerate engine over 3000 RPM.
If the value in either display field 1 or field 3
remains constant:
page Page 24
-46
, Evaluation of display group
36.
Pa
ge 58 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

24-52

Oxygen Sensor (O2S) heater behind
TWC, checking


Notes:

Connector for Oxygen Sensor (O2S) heater
(behind TWC) -Z29- (bank 1, sensor 2): 4-pin,
green
Connector for Oxygen Sensor (O2S) 2 (behind
TWC) -Z30- (bank 2, sensor 2): 4-pin, brown
Component locations page 24
-1

Required special tools and test equipment

VAG1551 or VAG1552 Scan Tool (ST) with
VAG1551/3 adapter cable
VAG1598/22 test box
Multimeter US1119 (Fluke 83 or equivalent)
VW1594 connector test kit
Wiring diagram
Pa
ge 65 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

Test requirements

Fuse for Oxygen Sensor (O2S) heater OK
Engine Coolant Temperature (ECT) at least
80 C (176 F)
Pa
ge 66 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

24-54

- Compare display and specified values (display
fields 3 and 4):

Display fields

1 2 3 4
Display group 40: Oxygen Sensor (O2S) heating (before and after TWC)
Display
xx.x
Htg.bC.ON/Htg.bC.OFF
xx.x
Htg.aC.ON/Htg.aC.OFF
Indicates Resistance of O2S heater
(before TWC)
(B1-S1 and B2-S1) O2S heater ON
or
O2S heater OFF
(before TWC)
(B1-S1 and B2-S1) Resistance of O2S heater
(after TWC)
(B1-S2 and B2-S2) O2S heater ON
or
O2S heater OFF
(after TWC)
(B1-S2 and B2-S2)
Range --- ---
0.0 - 65.0
---
Specified value --- ---
2.4 - 9.2
Htg.aC.ON

--- --- If not as specified page 24
-55
, Continuation
If displayed values are OK (as specified):

-
Press button.
-
Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
Pa
ge 68 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1