1999 AUDI TT engine

21-65


If wire connection is OK:
Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel Injection & Ignition,
Repair Group 24 - Check the following wire connection for open circuit and short circuit to
Ground (GND) and B+: Harness connector
terminal
VAG1598/31 test box
socket
2 104
- Repair open circuit or short circuit if necessary.
- Replace Engine Control Module (ECM):
Pa
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21-67

Note:
The charge air pressure sensor -G31- and wire
connections are monitored by the Engine Control
Module (ECM).

- Connect VAS5051 tester or VAG1551 scan tool
and select control module for engine electronics
using "address word 01". Engine must run at idle
for this:

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel
Injection & Ignition, Repair Group 01
- Check DTC memory of Engine Control Module
(ECM):

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel
Injection & Ignition, Repair Group 01 If a malfunction relating to the charge air
pressure sensor -G31- is indicated:

Checking voltage supply

- Disconnect harness connector at charge air
pressure sensor.
Pa
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gine code ATW
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21-68

- Switch ignition on.


Specified value: approx. 5 V
If specified value is not obtained:

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel Injection & Ignition,
Repair Group 24 - Connect VAG1598/31 test box to wiring harness -2- for Engine Control
Module (ECM), also connect ECM -1-. Connect Ground (GND) clamp -
3- to negative battery post.

If the specified value is met: - Check the following wire connections for open circuit and short circuit
to Ground (GND) and B+: Harness connector
terminal
VAG1598/31 test box
socket
1 108
3 98
- Repair open circuit or short circuit if necessary.
Pa
ge 28 of 42 Char
ge air s
ystem with turbochar
ger
(en
gine code ATW
)
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE02.21.3

21-69

Checking signal wire

- Connect harness connector at charge air
pressure sensor.

- Connect multimeter to socket 101 and socket
108 of test box for voltage measurement.

- Start engine and run at idle.


Specified value: approx. 1.90 V

- Bring up engine RPM by suddenly depressing
pedal.

Specified value: 2.00-3.00 V
If specified values are not obtained:

- Check the following wire connection for open circuit and short circuit to
Ground (GND) and B+: Harness connector
terminal
VAG1598/31 test box
socket
4 101
- Repair open circuit or short circuit if necessary.
Pa
ge 29 of 42 Char
ge air s
ystem with turbochar
ger
(en
gine code ATW
)
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE02.21.3

21-71

WARNING!

Use only approved air fittings to adapt shop
air supply line to VAG 1687 tester.

Special tool VAG 1687/1 pressure adapter,
installing (1.8L Turbo)

- Separate intake hose from Mass Air Flow (MAF)
sensor assembly.

Special tool VAG 1687/1 pressure adapter, installing (2.7L BiTurbo)
Repair Manual, Maintenance; Air cleaner housing, cleaning; Air cleaner element, replacing
- Insert VAG 1687/1 pressure adapter in intake hose -black arrow- using
existing clamp (as shown).
- Remove crankcase ventilation tube from intake hose at -white arrow-.
- Remove upper air cleaner housing and hoses to intake manifold as
necessary

- Insert VAG 1687/1 pressure adapter in intake hose -white arrow- using
existing clamp (as shown).
- Disconnect engine crankcase ventilation hose from intake manifold -
black arrow-.
-
Plug intake manifold fitting (for crankcase ventilation hose) with
appropriate hose and metal plug using clamps supplied with VAG
Pa
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(en
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)
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yp
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21-73

Special tool LKI9210 (Evaporative system
leak detector), preliminary set-up

- Connect smoke generator leads to vehicle
battery.

With system filled with smoke:
Special tool VAG 1687, connecting to pressure adapter VAG 1687/1
(1.8L Turbo)
For illustrations purposes VAG is shown lying in the engine compartment.
In practice the tool should be hung from the hood. - Turn valve to test -black arrow-.
- Press smoke generator button to fill system with smoke (see
instructions printed on tester).
- Remove smoke generator hose and connect VAG1687 quickly to
prevent smoke from leaking out Page 21
-73
.
- Connect VAG 1687 quickly to prevent smoke from leaking out.

VAG 1687 is shown connected to VAG 1687/1 -black arrow-
Shop air supply will be connected to VAG 1687 -at white arrow-
- Perform pressure test Page 21
-75
.
Pa
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ystem with turbochar
ger
(en
gine code ATW
)
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p://127.0.0.1:8080/audi/servlet/Dis
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yp
e=re
pair&id=AUDI.B5.GE02.21.3

21-74

Special tool VAG 1687, connecting to
pressure adapter VAG 1687/1 (2.7L BiTurbo)
For illustrations purposes VAG is shown lying in
the engine compartment. In practice the tool
should be hung from the hood.

- Connect VAG 1687 quickly to prevent smoke
from leaking out.

VAG 1687 is shown connected to VAG 1687/1 -black arrow-
Shop air supply will be connected to VAG 1687 -at white arrow-
- Perform pressure test Page 21
-75
.
Pa
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ystem with turbochar
ger
(en
gine code ATW
)
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p://127.0.0.1:8080/audi/servlet/Dis
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21-75

Performing pressure test:

- With outlet hose -1- of VAG 1687 connected to air pressure adapter:
- Attach shop air supply line to previously installed male fitting Page
21
-70
.

CAUTION! - Open valve -3- between regulator valve and gauge.
- Adjust test pressure up to 0.5 bar ( CAUTION below) by turning
regulator valve -2-.
DO NOT pressurize the system above 0.5 bar!Doing so may force oil into the intake system which can damage
the engine.
- Slowly open outlet valve -4- (after gauge) to test hose connections.
- Observe pressure gauge for a drop in pressure.
Pa
ge 39 of 42 Char
ge air s
ystem with turbochar
ger
(en
gine code ATW
)
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE02.21.3