2000 AUDI A8 ignition

24-61

Checking voltage supply

If there is no voltage:
Checking wiring - Disconnect 4-pin harness connector from Mass Air Flow sensor (MAF).
- Connect multimeter US 1119 (Fluke 83 or equivalent) between harness
connector terminals 1 and 3 (to ECM), using adapter cables from VW
1594 connector test kit.
Specified value: 9.0-14.5 volts
- Switch ignition off.
- Check wiring using applicable wiring diagram.
- Switch ignition off.
- Connect VAG 1598/22 test box to ECM harness connector Page 01
-
56
.

- Check wiring for open circuits between ECM/test box and 4-pin MAF
sensor harness connector.

Connector terminal 2 to ECM/test box socket 12
Connector terminal 4 to ECM/test box socket 13
Specified value: max. 1.5
Pa
ge 81 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

24-64

Checking

- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with ignition
switched on) 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-, -0- and -1- to input display group number 1, and
press -Q- button to confirm input.
Read Measuring Value Block 1 1 2 3 4

Indicated on display (1-4 = display fields)
Pa
ge 85 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

24-66
If NOT:

- Replace Engine Coolant Temperature (ECT)
sensor -G62-.

-
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.
Evaluation of display group 1 Display group: 1


Display field: 2
Possible cause
Corrective action
approx. -46.5 C
Open circuit or short circuit in wiring to B+ - Check wiring Page 24
-66
approx. 141.0 C
Short circuit to Ground

Checking wiring

- Connect VAG 1598/22 test box to ECM harness
connector Page 01
-56
.
Pa
ge 88 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

24-70

Checking

- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with ignition
switched on) 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-, -0- and -4- to input display group number 4, and
press -Q- button to confirm input.
Read Measuring Value Block 4 1 2 3 4

Indicated on display (1-4 = display fields)
Pa
ge 93 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

24-72
Evaluation of display group 4 Display group: 4


Display field: 4
Possible cause
Corrective action
-46.5 C
Open or short circuit in wiring to B+ Page 24
-72
, check wiring
141.0 C
Short circuit to ground
approx. ambient temperature Signal intermittently interrupted
Continuation of test, page Page 24
-74
- Check IAT sensor

Wiring, checking:

- Switch ignition off.

- Connect VAG 1598/22 test box to ECM harness
connector Page 01
-56
.

- Disconnect 2-pin connector from Intake Air
Temperature (IAT) sensor -G42-.

- Check wiring for open circuit between ECM/test box and 2-pin IAT harness
connector (to ECM).

Connector terminal 1 to ECM/test box socket 54
Connector terminal 2 to ECM/test box socket 67
Pa
ge 95 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

24-77

Voltage supply to Engine Control
Module (ECM)


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

Checking

- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with ignition
switched on) 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.
Pa
ge 103 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

24-79
Evaluation of display group 4 Display group: 4


Display field: 2
Possible cause
Corrective action
No VAG 1551 display
Fuse for ECM faulty- Replace fuse
Open circuit in wiring- Voltage supply at terminal 15 Page 24
-
80

Displayed value changes between 10.0-14.5
V
Intermittent connection - Voltage supply at terminal 30 Page 24
-
79

0.0-10.0 V
Battery
discharged/faulty Voltage regulator faulty - Check battery
- Check generator
- Check voltage regulator
14.5-16.5 V Generator faultyVoltage regulator faulty - Check generator
- Check voltage regulator

Checking voltage supply at terminal 30

- Switch ignition off.

- Connect VAG 1598/22 test box to ECM harness
connector Page 01
-56
.
Pa
ge 106 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

24-80
If voltage is NOT OK:

- Check wiring according to applicable wiring
diagram.

Checking voltage supply at terminal 15

- Switch ignition off.

- Connect VAG 1598/22 test box to ECM harness
connector Page 01
-56
.

- Connect multimeter between ECM/test box
sockets 1 (B+) and 2 (Ground), using adapter
cables from VW 1594 connector test kit.

- Switch ignition on, and check voltage.

Specified value: 10-14.5 volts
If voltage is NOT OK:

- Check wiring according to applicable wiring
diagram.

-
Check readiness code Page 01
-59
. If
Diagnostic Trouble Code (DTC) memory has
been erased, or ECM was disconnected,
Pa
ge 108 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