AUDI TT 1995 8N / 1.G AEB ATW Engines Charge Air System With Turbocharger Workshop Manual

21-46


Charge air system with
turbocharger (engine code
ATW)

Checking mechanical recirculation valve

Notes:

The mechanical recirculation valve is located in
front of the turbocharger. It is opened by
vacuum via the recirculating valve for
turbocharger -N249- during deceleration, idle
and part throttle. This produces a reduction of
the charge air pressure in front of the throttle
valve which keeps the turbocharger spinning at
a higher RPM.
Check the recirculation valve in case of reduced
performance or part throttle hesitation.

Special tools and equipment

VAG1390
Pa
ge 1 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

21-47

Test sequence

If recirculation valve does not open or close or valve plate does not seal
correctly when valve is closed: - Attach VAG1390 vacuum pump to recirculation valve.
- Operate vacuum pump.

Recirculation valve must open (arrow)
- After approx. 30 seconds, operate vent valve on vacuum pump.
Recirculation valve must close (arrow)
- Replace recirculation valve. Secure connections of recirculation valve
using screw type clamps.
Pa
ge 2 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

21-48


Recirculating valve for turbocharger -
N249-, checking

Special tools and equipment

VAG1526A
VAG1527B
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3A
Pa
ge 3 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

21-49

Note:
The recirculating valve for turbocharger -N249-
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 If a malfunction relating to the recirculating valve
for turbocharger -N249- is displayed:

- Disconnect hoses from valve; harness connector
remains connected.

- Attach assisting hose to one connection of
valve.
Pa
ge 4 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

21-50

- Initiate output Diagnostic Test Mode (DTM) and
activate the recirculating valve for turbocharger -
N249-:

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel
Injection & Ignition, Repair Group 01 Output Diagnostic Test Mode Recirc. valve for turbochar
ger -N249

Indicated on display
If valve does not click:
If valve does not open and close properly:
Checking internal resistance Valve must click...
...and must open and close (can be tested by blowing into assisting
hose).
- Check internal resistance of valve.
- Replace recirculating valve for turbocharger -N249-.
- Disconnect harness connector at valve.

- Connect multimeter at valve for resistance measurement.

Specified value: 27-30
Pa
ge 5 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

If specified value is not obtained:
- Replace recirculating valve for turbocharger -N249-.
Pa
ge 6 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

21-51
If the specified value is attained:

- Check voltage supply

Checking voltage supply

Note:
Voltage is supplied to the recirculation valve via
the Fuel Pump (FP) relay.

Test requirement

Fuse for recirculation valve OK

- Disconnect harness connector at valve.

- Connect VAG1527B voltage tester as follows:Harness connector
terminal
Measure to
1 Engine Ground (GND)
- Operate starter briefly.

LED must light.
Pa
ge 7 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

21-52
If LED does not light:

- Check wire connection from terminal 1 to Fuel
Pump (FP) relay via fuse for an open circuit":

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
- Repair open circuit if necessary.
If wire connection is OK:

- Check Fuel Pump (FP) relay:

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel
Injection & Ignition, Repair Group 24 If LED lights:

- Check activation:

Checking activation

- Connect VAG1527B voltage tester to connector terminals 1 (B+) and 2.
-
Initiate output Diagnostic Test Mode (DTM) and activate the
Pa
ge 8 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

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel Injection & Ignition,
Repair Group 01 recirculating valve for turbocharger -N249-:
LED must blink.
Pa
ge 9 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

21-53
If LED does not blink or if it remains constantly
lit:

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM:

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel
Injection & Ignition, Repair Group 24

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
2 105
- Repair open circuit or short circuit if necessary.
- Replace Engine Control Module (ECM):
Pa
ge 10 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