1999 AUDI A4 engine

24-62

- Connect multimeter to terminal 2 of connector
and engine Ground (GND) for voltage
measurement.

- Operate starter briefly.

Specification: approx. battery voltage

Note:
Voltage is supplied to Mass Air Flow (MAF)
sensor from Fuel Pump (FP) relay.
If there is no battery voltage.

- Check wire connection from terminal 2 of
connector to Fuel Pump (FP) relay via fuse for
open circuit and short circuit to Ground (GND),
repair if necessary.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
Pa
ge 72 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-65

Voltage supply for Mass Air Flow (MAF)
sensor, checking (Bosch MAF sensor)

Note:
Voltage is supplied to Mass Air Flow (MAF) sensor from Fuel Pump (FP)
relay.
If there is no battery voltage.
Electrical Wiring Diagrams, Troubleshooting & Component Locations - Disconnect connector from Mass Air Flow (MAF) sensor.
- Connect multimeter to terminal 2 of connector and engine Ground
(GND) for voltage measurement.
- Operate starter briefly.
Specification: approx. battery voltage
- Check wire connection from terminal 2 of connector to Fuel Pump (FP)
relay via fuse for open circuit and short circuit to Ground (GND), repair
if necessary.
Pa
ge 75 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-69


Display fields

1 2 3 4
Display Group 002: Intake air mass at idling speed with engine at operating temperature
Display xxx RPM xx.x %
x.x ms
xxx.x g/s
Indicates Engine
speed
(in steps of
40 RPM) Load
Average injection
period Air mass
Work range min.: 750
rpm
max.: 6800
rpm min.: 15
%
max.:
175 % min.: 2.0 ms
max.: 19.0 ms min.: 3.0 g/s
max.: approx: 225g/s
Specification 750 - 850
rpm 15.0 -
25.0 % 2.0 - 4.0 ms1.
3.0 - 4.5 g/s
Note --- ---
If readout does not match
specification, see table for display
field 3 Page 24
-70

If readout does not match
specification, see table for display
field 4 Page 24
-71

If the specification is obtained:

-
Press button.
- Press buttons -0- and -6- to select function "End
Output" and confirm entry with -Q- button.
Pa
ge 79 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-70
Reading Display Group 002 Display field
3
Possible cause of malfunction
Corrective action
Less than 2.0
ms
Lower values can only occur when vehicle is on fuel-
shut off (overrun)
More than 4.0
ms Load on engine due to ancillaries- Eliminate load (air conditioner, power
steering, alternator)

Rough idle (engine not running on all cylinders)- Check spark plugs
- Check fuel injectors Page 24
-39


Throttle Valve Control Module -J338 faulty- Check Throttle Valve Control Module
Page 24
-139

Pa
ge 81 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-71
Reading Display Group 002 Display field
4
Possible cause of malfunction
Corrective action
Less than 3.0
g/s
Large quantity of un-metered air between intake manifold
and Mass Air Flow (MAF) sensor
Voltage supply to Mass Air Flow (MAF) sensor or wiring to
Engine Control Module (ECM) - Check intake system for leaks (un-
metered air) Page 24
-76

- Check voltage supply and wiring Page 24
-72

More than 4.5
g/s
Load on engine due to accessories- Eliminate load (A/C, power steering,
generator)

Voltage supply to Mass Air Flow (MAF) sensor or wiring to
Engine Control Module (ECM) - Check voltage supply and wiring Page
24
-72

Pa
ge 82 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-72

Checking voltage supply to Mass Air Flow
(MAF) sensor

- Disconnect harness connector from air mass
meter.

Note:
The mass air flow sensor receives its voltage supply via the fuel pump
relay.
If the reading does not match the battery voltage:
Electrical Wiring Diagrams, Troubleshooting & Component Locations - Connect hand-held multimeter (voltage measurement range) between
engine Ground (GND) and socket 2 of connector.
- Operate starter briefly.
Specification: approx. battery voltage
- Check for open circuit or short to Ground (GND) in wiring between fuel
pump relay and socket 2 on connector via fuse. Repair if necessary.
Pa
ge 83 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-73


Note:
Socket 3 on the connector is the Ground (GND) connection from the
engine control module.
If the specification is not attained: - Connect hand-held multimeter (voltage measurement range) between
sockets 2 and 3 of connector.
- Operate starter briefly.
Specification: approx. battery voltage
- Check wiring Page 24
-74
.

If the specification is not attained: - Connect hand-held multimeter (voltage measurement range) between
sockets 3 and 4 of connector.
- Switch ignition on.
Specification: approx. 5 V
- Check wiring Page 24
-74
.
Pa
ge 84 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-74

Checking wiring for mass air flow sensor

Note:
The wiring test includes also testing the signal
wire.

- Connect VAG1598/31 test box to wiring harness
for engine control module. Do not connect to the
engine control module itself Page 24
-20
.

- Check for open circuit and short to B+ or Ground (GND) in the following
wiring connections: Connector for MAF sensor -G70,
socket
VAG1598/31 test box,
socket
3 27
4 53
5 29
Pa
ge 85 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1