1996 AUDI A4 relay

24-57

Checking activation

Note:
Diode test lamps with a low current draw do not go out completely but
continue to glow faintly until the starter is operated.
If the diode test lamp does not light up, test the wiring as follows: - Connect diode test lamp VAG1527 between B+ and contact 16 on
relay panel (Ground connection via engine control module).
- Operate starter briefly.
- The diode test lamp should light up and remain lit when the starter is
operated.
- If activation, wiring and power supply for fuel pump relay are OK but
fuel pump relay still does not pick up, replace fuel pump relay.
- Connect VAG1598/31 test box to wiring harness for engine control
module. Do not connect to the engine control module itself Page 24
-
20
.
Pa
ge 67 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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pair&id=AUDI.B5.FU04.24.1

24-58

- Connect hand-held multimeter between contact
16 on relay panel and socket 65 on the test box,
then test wiring for open circuits.

- Rectify open circuit if necessary.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
- If there is no open circuit and the diode test lamp
still does not light up:

- Replace Engine Control Module (ECM) Page
24
-24
.

- Reinstall fuel pump fuse.
Pa
ge 68 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

24-62

- 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

24-72

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