engine AUDI A4 1997 B5 / 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

21-49

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

21-51
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

21-53
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

21-58

Note:
The height of the charge air pressure should be
determined using the VAG1397/A turbocharger
test tool, the VAS5051 tester or the VAG1551
Scan Tool is used to determine whether the
charge air pressure is also being recognized in
the control module.

Specification on VAG1397A: 1.450-1.700 bar
Read Measuring Value Block 115 3000 RPM
42%
1770 mbar
1770 mbar

If the specification is exceeded or not met:
Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel Injection & Ignition,
Repair Group 01
Specified value on VAS 5051 or VAG 1551 Display field 4: 1450-1700
mbar
- Check DTC memory of Engine Control Module (ECM):
Pa
ge 16 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

21-59
charge air pressure regulation Diagnostic Trouble Codes (DTC) Diagnostic Trouble
Code (DTC) Charge air pressure
Possible causes
Charge air pressure
too low
Measured value below
1.450 bar or 1450 mbar
Wastegate bypass regulator valve -N75- faultyWire to wastegate bypass regulator valve -N75- faultyCharge air pressure regulator valve in turbocharger is stuck in
open position Leak between turbocharger and intake manifoldMechanical recirculation valve faultyTurbocharger malfunctioning
Charge air pressure
too high
1)
Measured value above
1.700 bar or 1700 mbar
Vacuum diaphragm for charge air pressure regulator valve
faulty Hoses to vacuum diaphragm for charge air pressure regulation
valve (via wastegate bypass regulator valve -N75-) leaky Charge air pressure regulator valve in turbocharger is stuck in
closed position
1) If charge air pressure is too high, the fuel supply is shutoff to protect the engine. The engine misfires at high engine
speeds.
Pa
ge 17 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

21-61

Note:
The wastegate bypass regulator valve -N75- 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 wastegate bypass
regulator valve -N75- is indicated:

- Disconnect hoses from valve; harness connector
remains connected.

-
Attach assisting hose to one connection of
Pa
ge 19 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

21-63
If specified value is not obtained:

- Replace wastegate bypass regulator valve -N75-
.
If the specified value is met:

Checking voltage supply

If LED does not light:
Electrical Wiring Diagrams, Troubleshooting & Component Locations - Connect VAG1527B voltage tester as follows:Harness connector
terminal
Measure to
1 Engine Ground (GND)
- Operate starter briefly.

LED must light.
- Check wire connection from terminal 1 to Fuel Pump (FP) relay via
fuse for open circuit:
- Repair open circuit if necessary.
Pa
ge 22 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

21-65


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
ge 24 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

21-67

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
ge 26 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