1999 AUDI A6 engine

24-24

Checking HO2S reference voltage

- Disconnect 4-pin connector -1- (brown) for
HO2S -G39-.

If voltage is NOT OK:
If voltage is OK: - Connect multimeter US 1119 (Fluke 83 or equivalent) between harness
connector terminals 3 and 4 (to ECM), using adapter cables from VW
1594 connector test kit.
- Start engine and measure voltage.
Specified value: 0.40-0.50 volts
- Switch ignition off.
- Check HO2S wiring Page 24
-25
- Replace Heated Oxygen Sensor (HO2S) -G39-.
Pa
ge 35 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1

Engine Coolant Temperature (ECT) at least
85 C (185 F)
Pa
ge 39 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1

24-28

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-, -4- and -1- to input display group number 41, and
press -Q- button to confirm input.
Read Measuring Value Block 41 1 2 3 4

Indicated on display (1-4 = display fields)
Pa
ge 40 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1

Engine Coolant Temperature (ECT) at least
85 C (185 F)
Pa
ge 49 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1

24-36

Function test

- 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 -6- to input display group number 36, and
press -Q- button to confirm input.
Read Measuring Value Block 36 1 2 3 4

Indicated on display (1-4 = display fields)
Pa
ge 50 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1

24-38

Continuation
If displayed values are NOT OK (not as
specified):

- Road test to condition oxygen sensor (eliminate
possible contamination) and repeat test.
If the values in display fields 1 and 2 are still
NOT OK:

- Check Oxygen Sensor (O2S) heater Page 24
-
43
.

- Briefly accelerate engine over 3000 RPM.
If the value in display field 1 remains constant:
page Page 24
-39
, Evaluation of display group
36.
Pa
ge 52 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1

24-40

Checking HO2S reference voltage

- Disconnect 4-pin connector (black) for Oxygen
Sensor (O2S) behind Three Way Catalytic
Converter (TWC) -G108-.

If voltage is NOT OK:
If voltage is OK: - Connect multimeter US 1119 (Fluke 83 or equivalent) between harness
connector terminals 3 and 4 (to ECM), using adapter cables from VW
1594 connector test kit.
- Start engine and measure voltage.
Specified value: 0.40 to 0.50 volts
- Switch ignition off.
- Check HO2S wiring Page 24
-41
- Replace HO2S behind TWC -G108-.
Pa
ge 54 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1

Engine Coolant Temperature (ECT) at least
85 C (185 F)
Pa
ge 58 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1