AUDI TT 1997 8N / 1.G AEB ATW Engines Charge Air System With Turbocharger User Guide

21-54

Turbocharger and charge air pressure
regulator valve, checking


Special tools and equipment

VAG1397A

VAS5051 with VAG5051/1
orVAG1551 with VAG1551/3A
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Test requirements

All hoses and wires have been checked for
proper seating and seal.
DTC memory checked

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel
Injection & Ignition, Repair Group 01

Output Diagnostic Test Mode (DTM)
performed

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel
Injection & Ignition, Repair Group 01

Vehicle tester VAS 5051 or VAG 1551
connected.

Test sequence

WARNING!

To reduce the risk of accident or injury while
carrying out tests and measurements during
a road test, observe safety precautions
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- Using T-piece connect test hose from VAG1397A Turbocharger Tester
between intake manifold and fuel pressure regulator.
- Guide test hose over rear corner of hood, through passenger side
window and into vehicle interior.
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Notes: - Turn turbocharger tester on and select measuring range -I- (absolute
pressure).
- Connect test hose to connection barb -I-.
Hoses must be properly connected and there must be no possibility of
leaks, otherwise incorrect readings may result. Make sure that the test hose is not pinched at the hood or at the side
window. By pressing memory button "M" on turbocharger tester, the last test
value is saved until either memory button "M" is pressed again or the
turbocharger tester is shut-off. A blinking comma in the display field indicates that a value has been
saved. An arrow appears in the top left corner of the display field if the
turbocharger tester battery voltage drops below the permitted
threshold. Before testing, drive vehicle rapidly for at least 3 km on a road that
does not require stopping (i.e. traffic lights or similar). A second technician is required because the indicated values must be
read out while the vehicle is being driven.
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Rapid data transferSelect 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 Measuring Value Block
Q
Input displa
y group number XXX

When indicated on display:
- Press buttons -0-, -0- and -4- to select "display group number 004" and
press -Q- button to confirm input.
Read Measuring Value Block 4
1
2
3
4

Indicated on display
Do not continue with test until intake air temperature in display field 4 is
20-50 C if necessary, warm up vehicle by driving. - Press -C- button.
Read Measuring 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
1
2
3
4

Indicated on display (1-4 = display fields)
- Accelerate vehicle in 3rd gear at full throttle from 2000 RPM and
observe tachometer.
- At approx. 3000 RPM, press the print button on the VAS5051 or
VAG1551 and simultaneously press the memory button -M- on the
VAG1397A.
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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):
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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.
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Wastegate bypass regulator valve -N75-,
checking

Special tools and equipment

VAG1526A
VAG1527B
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3A
Pa
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)
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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
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valve.
Pa
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gine code ATW
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