fuse diagram AUDI A4 1999 B5 / 1.G AHA Engine Multiport Fuel Injection And Ignition System Workshop Manual

24-68

Mass Air Flow (MAF) sensor, checking


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
All electrical consumers switched off (coolant
fan must not run during test).
A/C must be switched off
Fuse for MAF sensor OK
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24-96
If the fuel pump does not respond:

- Check fuel pump relay actuation page 24
-
99
.
If the LED test light does not light up:

- Repeat test at other terminal of fuse 28.

If the LED light still does not light up:
- Check wiring for open or short circuits between fuse 28 and terminal 30
at relay position 6, using the applicable wiring diagram. Repair wiring
as necessary.

Specified value: max. 1.5

Note:
This step lets the fuel pump run without the engine running. The closed
throttle position switch must be closed during the test, or the selected fuel
injector will discharge fuel when it is actuated 5 times. - Connect VAG1527B LED voltage tester between Ground and one of
the two terminals for fuse 29.
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ge 122 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
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24-97
If the LED test light does not light up:

- Repeat test at other terminal of fuse 29.

If the LED test light still does not light up:
- Check wiring for open circuit between fuse 29 and terminal 30 at relay
position 6, using the applicable wiring diagram. Repair wiring as
necessary.

Specified value: max. 1.5

Note:
This step lets the fuel pump run without the engine running. The closed
throttle position switch must be closed during the test, or the selected fuel
injector will discharge fuel when it is actuated 5 times. - Connect VAG1527 LED voltage tester between Ground and one of the
two terminals of fuse 34.
- Initiate output Diagnostic Test Mode (DTM) and advance to test of
cylinder 1 fuel injector -N30- page 01
-51
.

LED test light must light up
Fuel pump relay must be activated
Pa
ge 124 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
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24-98
If the LED test light does not light up:

- Repeat test at other terminal of fuse 34.

If the LED test light still does not light up:
- Check wiring for open circuit between fuse 34 and terminal 31 at relay
position 6, using the applicable wiring diagram. Repair wiring as
necessary.

Specified value: max. 1.5
Pa
ge 126 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

24-121

Checking EVAP canister purge regulator
valve voltage supply

Test conditions

Fuse for EVAP canister purge regulator
valve OK

- Disconnect harness connector from EVAP
canister purge regulator valve.

If LED test light does not light:
If wiring is OK: - Connect VAG1527B LED voltage tester between connector terminal 1
(B+) and engine Ground.
- Operate starter motor.
Specified value: LED must light up
- Check wiring for open circuit between connector terminal 1 and fuse,
according to wiring diagram; repair if necessary.

Specified value: 1.0 max.- Check fuel pump relay page 24
-95
.
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port Fuel In
jection
(MFI
) and i
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24-125

Voltage supply, checking

If LED tester does not light: - Disconnect harness connector for LDP -V144-.
- Connect VAG1527B LED voltage tester between connector terminal 3
(B+) and engine Ground.
- Start engine and run engine at idle.
LED must light up.
- Check fuse for LDP -V144-.
- Check wiring for open circuit between terminal 3 and fuse, according to
wiring diagram.

Specified value: max. 0.5 .- Check fuel pump relay and signal to relay page 24
-95
.
Pa
ge 162 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