check AUDI A4 1995 B5 / 1.G APB Engine Charge Air System With Turbocharger Workshop Manual

21-9

Turbocharger and charge pressure
regulating valve, checking


Safety notes
Note the following points if test equipment has to
be used during a road test:

WARNING!

Test equipment must always be secured on
the rear seat and operated from there by a
second person.
If test equipment is operated from the front
passenger seat, the occupant could be
injured by the passenger's airbag in an
accident.

Special tools, testers and auxiliary items
Turbocharger tester VAG 1397 A
VAG 1551 Scan Tool or VAG 1552 with cable
VAG 1551/3
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21-13

Charge air pressure regulation,
checking


Special tools and equipment

or
Test requirement:
WARNING!
VAS 5051 with VAG 5051/1VAG 1551 with VAG 1551/3ACoolant Temperature at least 80 C. During a road test in an airbag-equipped vehicle, test equipment
must always be fastened to and operated from the rear seat by a
second technician. When driving or riding in an airbag-equipped vehicle, NEVER hold
the scan tool or other test equipment in your hands or lap while in
motion. Objects between you and the airbag increase the risk of
injury in an accident.
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1
2
3
4
- Check charge air pressure regulation.
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21-16

- Select measuring value block 117.

- Check function of accelerator pedal in display
field 2 by briefly depressing pedal to Wide Open
Throttle.

Display fields

1 2 3 4
Display group 117: Charge air pressure regulation
Display 1 RPM
% % mbar
Indicated Engine speed (RPM)
Accelerator pedal
position Throttle valve angle Specified charge air
pressure
Specified value
0...100
Note: If the specified value 100% is not reached at
Wide Open Throttle (WOT):

- Check accelerator pedal.

- Select measuring value block 116.
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21-17

- Check correction factors in display fields 2 to
4.

Display fields

1 2 3 4
Display group 116: Charge air pressure regulation
Display 1 RPM
% % mbar
Indicated Engine speed (RPM)
Correction factor
Fuel Correction factor
Coolant temp. Correction factor
Intake air temp.
Specified value


Note: If display field 2 indicates a correction factor <0
%, fuel quality is probably incorrect.

- Fill tank with prescribed fuel quality.
If display field 3 indicates a correction factor <0
%, coolant temperature is too high (heat warning
lamp lit in instrument cluster) or the Engine
Control Module is receiving an incorrect
temperature signal from the instrument cluster.

- Check coolant temperature display.

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measuring value blocks:

- Check the charge air pressure sensor -G31-.
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21-19


Recirculating valve for turbocharger -
N249-, checking

Special tools and equipment

VAG 1526A
VAG 1527B
VAG 1594A
VAG 1598/31
VAS 5051 with VAG 5051/1
- or
VAG 1551 with VAG 1551/3A
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21-20

Note:
The recirculating valve for turbocharger -N249
and wire connections are monitored by the
Engine Control Module (ECM).

- Connect VAS 5051 tester or VAG 1551 scan
tool and select control module for engine
electronics using "address word" 01. Engine
must run at idle for this.

Repair Manual, 2.7 Liter V6 5V BiTurbo Fuel
Injection & Ignition, Engine Code(s): APB, Repair Group 01


- Check DTC memory of Engine Control Module
(ECM).

Repair Manual, 2.7 Liter V6 5V BiTurbo Fuel
Injection & Ignition, Engine Code(s): APB, Repair Group 01

If a Diagnostic Trouble Code (DTC) relating to
the recirculating valve for turbocharger -N249- is
displayed:

-
Disconnect hoses from valve; harness connector
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21-21

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

Repair Manual, 2.7 Liter V6 5V BiTurbo Fuel
Injection & Ignition, Engine Code(s): APB, Repair Group 01

Output diagnostic test mode Recr. valve for turbocharger -N249

Indicated on display
If valve does not click:
If valve does not open and close properly: 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-.
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21-22

Checking internal resistance

- Disconnect connector at valve.

If specified value is not obtained:
If the specified value is met: - Connect multimeter at valve for resistance measurement.

Specified value: 27 ... 30
- Replace recirculating valve for turbocharger -N249-.
- Check voltage supply
Pa
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