1996 AUDI A4 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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21-10

Requirements for test:

Diagnostic Trouble Code (DTC) memory has
been interrogated

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


Output Diagnostic Test Mode (DTM) has
been performed
Engine oil temperature at least 60 C

All vacuum connections airtight

- Loosen bolts -arrows- and remove engine cover panel -B-.
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- Connect T-piece with measuring hose of turbocharger tester VAG 1397
A to fuel pressure regulator -arrow-.
- Route measuring hose under rear edge of hood and into passenger
compartment via right-hand window.
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21-11


Notes: - Switch on turbocharger tester and set measuring range selector switch
to position -I- (absolute pressure).
- Connect measuring hose to connection -I-.
Hose connections must be completely airtight, otherwise
measurements will not be correct. Ensure that measuring hose is not pinched at hood or side window.Pressing memory key M on turbocharger tester will store the last
measured value until memory key M is pressed again or tester is
switched off. The decimal point in the display flashes to indicate that the value is
being stored. If the battery voltage of the turbocharger tester drops below the
minimum level, an arrow will appear at the top left of the display. Before performing the test, drive the vehicle at a brisk speed for at
least 3 km (without stopping at traffic lights etc.). A second mechanic is required to note the readings on the tester
when the vehicle is moving. Observe safety notes Page 21
-9 .
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21-12

- Accelerate vehicle from 2000 RPM at full throttle
in fourth gear, and watch rev counter.

Note:
If no charge pressure is obtained and a throbbing noise can be heard in
the engine compartment, the causes can be as follows: - Press memory key -M- on turbocharger tester at 3000 RPM.

Specification: 1.550 ... 1.650 bar
Air recirculation valve faulty.Vacuum line to air recirculation valve leaking or has become
disconnected.
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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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21-14

Test sequence

Repair Manual, 2.7 Liter V6 5V BiTurbo Fuel Injection & Ignition,
Engine Code(s): APB, Repair Group 01
- 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.
Rapid data transfer
HELP
Select function XX

When indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Read measurin
g value block
Q
Input displa
y group number XXX

When indicated on display
- Press buttons -1-, -1- and -5- to select "display group number 115" and
press -Q- button to confirm input.
Read Measuring Value Block 115

Indicated on display (1...4 display fields)
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1
2
3
4
- Check charge air pressure regulation.
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