1996 AUDI A4 fuel pressure

21-16


Charge pressure leak test with
VAG 1687

Intake system, checking for leaks using
VAG 1687 Diagnostic Tool

Diagnostic trouble codes (DTCs) related to fuel
trim, charge pressure or mass air flow (MAF)
may be caused by:

Leaking (worn/torn) intake hoses during charge
conditions
Incorrectly torqued or improperly placed clamps
on intake hoses etc. causing leaks during
charge conditions

Check the charge air pressure system using the VAG 1687 Charge air
system tester.
Special tool VAG 1687 Charge air system tester preliminary set-up

- Back off pressure regulator knob -2- of VAG 1687 fully to protect gauge
when shop air supply is applied to assembly.
Pa
ge 1 of 34 Char
ge pressure leak test with VAG 1687
11/21/2002 htt
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21-30

Checking power supply

Note:
The power supply for the recirculating valve is via
the fuel pump relay.

Test requirements:

Fuse for recirculating valve OK.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder

Fuel pump relay OK.

Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo Fuel
Injection & Ignition, Engine Code(s): AWM, Repair Group 24


- Disconnect wiring connector from valve.

- Connect voltage tester VAG 1527 B as follows:Connector
Measure to
Pa
ge 19 of 34 Char
ge pressure leak test with VAG 1687
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21-31
If the LED does not light up:

- Check wiring from contact 1 on connector via
fuse to fuel pump relay for an open circuit:

Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder
- Repair open circuit, if necessary.
If the LED lights up:

- Check actuation.

Checking actuation

- Connect voltage tester VAG 1527 B to contacts 1 (positive) and 2 of
connector.
- Initiate output Diagnostic Test Mode (DTM) and activate recirculatiing
valve for turbocharger -N249-.
The LED must flash.
Pa
ge 21 of 34 Char
ge pressure leak test with VAG 1687
11/21/2002 htt
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yp
e=re
pair&id=AUDI.B5.GE06.21.2

21-32
If the LED lamp does not flash or if it lights up
continuously:

- Connect VAG 1598/31 test box to wiring
harness leading to engine control module;
engine control module should not be connected:

Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo Fuel
Injection & Ignition, Engine Code(s): AWM, Repair Group 24


If the wiring is OK: - Check for open circuit and short to positive or Ground in following
wiring connection: Connector
Contact
Test box VAG 1598/31
2 105
- Repair any open/short circuit as necessary.
- Replace engine control module.
Pa
ge 22 of 34 Char
ge pressure leak test with VAG 1687
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE06.21.2

21-36

Checking power supply

Test requirements:

Fuse for wastegate bypass regulator valve
OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder

Fuel pump relay OK.

Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo Fuel
Injection & Ignition, Engine Code(s): AWM, Repair Group 24


- Connect voltage tester VAG 1527 B as follows:Connector
contact
Measure to
1 Engine Ground
- Operate starter briefly.

LED must light up.
Pa
ge 26 of 34 Char
ge pressure leak test with VAG 1687
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE06.21.2

21-37
If the LED does not light up:

- Check wiring from contact 1 on connector via
fuse to fuel pump relay for open circuit:

Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder
- Repair open circuit, if necessary
If the LED lights up:

- Check actuation.

Checking actuation

- Connect voltage tester VAG 1527 B to contacts 1 (positive) and 2 of
connector.
- Initiate output Diagnostic Test Mode (DTM) and actuate Wastegate
Bypass Regulator valve -N75-.
Output Diagnostic Test Mode

Display
Pa
ge 27 of 34 Char
ge pressure leak test with VAG 1687
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE06.21.2

21-38
If the LED lamp does not flash or if it lights up
continuously:

- Connect VAG 1598/31 test box to wiring
harness leading to engine control module;
engine control module should not be connected:

Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo Fuel
Injection & Ignition, Engine Code(s): AWM, Repair Group 24


If the wiring is OK: - Check for open circuit and short to positive or Ground in following
wiring connection: Connector
Contact
Test box VAG 1598/31
2 104
- Repair any open/short circuit as necessary.
- Replace engine control module.
Pa
ge 29 of 34 Char
ge pressure leak test with VAG 1687
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE06.21.2

21-41


If specified value is not attained: - Connect multimeter between contacts 1 and 3 of connector to measure
voltage.
- Switch ignition on.
Specified value: approx. 5 V

Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo Fuel Injection & Ignition,
Engine Code(s): AWM, Repair Group 24
- Connect VAG 1598/31 test box to wiring harness leading to engine
control module; engine control module must also be connected.
Pa
ge 32 of 34 Char
ge pressure leak test with VAG 1687
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE06.21.2