1998 AUDI A4 check engine

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

24-76

Air system for leaks (un-metered air),
checking


Check with engine leak detector spray G 001
800 A1

CAUTION!

Part numbers are for reference only, always
check with your parts department for latest
information.

Notes:

The vacuum in the intake system will cause the
leak detector spray to be drawn in with the
outside air. The leak detector spray reduces the
ignitability of the mixture. This leads to a drop in
engine speed and to a significant increase of
the CO content.
The safety precautions listed on the container
must be adhered to.

- Connect VAG1551 (or VAS 5051) and select
engine electronics control module with the
"Address word" 01. When doing this the engine
must be running at idling speed. (Connect scan
tool and selecting engine electronics control
module Page 01
-9 .)
Pa
ge 87 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

24-78
If the engine speed drops:

-
Press button.
- Press buttons -0- and -6- to select function "End
Output" and confirm entry with -Q- button.

- Check sprayed areas of intake system for leaks
and rectify if necessary.
Pa
ge 90 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