AUDI A6 2000 C5 / 2.G AEB ATW Engines Turbocharger System User Guide

21-10

Charge air pressure control (via load
signal), checking


WARNING!

Always use a second technician to take
measurements via the VAG1397A
turbocharger tester when test-driving vehicle
for this test.
Follow "WARNING!" Page 21
-5 .

Note:
If VAG1551 scan tool is not available, use
VAG1552 mobile scan tool instead.

- Unclip Data Link Connector (DLC) cover.

- Using VAG1551/3 adapter, connect VAG1551 Scan Tool (ST) or
VAG1552 mobile scan tool.
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VAG - ON BOARD DIAGNOSTIC
HELP
1 - Rapid data transfer2 - Blink code output

Indicated on display
1)
1) Operating modes 1 and 2 are displayed alternately
Note:
If nothing appears on display:
Scan tool operating instructions
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21-11

- Press button 1 to select "Rapid data transfer"
operating mode 1.

- Start engine.Rapid data transfer
HELP
Select function XX

Indicated on display
Rapid data transfer
Q
01 - En
gine Electronics

- Press buttons -0- and -1- to insert "Engine Electronics" address word
01.
- Press -Q- button to confirm input.
06A906018.. 1.8l R4/5T MOTR HS 0.. Codin
g 04000
WSC 12345

VAG1551 scan tool display indicates control module coding.
-
Press button.
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block"
function 08.
- Press -Q- button to confirm input.
Read Measuring Value Block
HELP
Input displa
y group number XXX

Indicated on display
- Press buttons -1-, -1- and -4- to input display group number 114 (114).
- Press -Q- button to confirm input.
Read Measuring Value Block 114

The "Read Measuring Value Block" displays four display fields.
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1
2
3
4
Interpreting values 1-4 in each display field Page 21
-12
.
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21-12

Interpreting display fields Read Measuring Value Block 114 1
2
3
4

Indicated on display:
Specification
Deviation between display field 2 and 3: 0.3 ms (max.)
Note:
If the OBD for the Engine Control Module (ECM) recognizes Diagnostic
Trouble Codes (DTCs) in charge air pressure regulation, duty cycle
(display field 4) will indicate a constant 5%.
Display
field Description
1 Not applicable
2 Specified engine load (after correction)
3 Current engine load
4 Duty cycle (actuation of wastegate bypass regulator valve
-N75-)
- Note values in display field 2 and 3 while vehicle is under steady
acceleration.
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21-13
Diagnostic Trouble Codes (DTC) for charge air pressure regulation Diagnostic
Trouble Code
(DTC) VAG1397A Display
VAG1551 Display
Possible causes
Charge air
pressure too
low
Measured value below 1.37
bar (19.9 psi) (vehicles with
manual transmission)
Measured value below 1.30
bar (18.9 psi) (vehicles with
automatic transmission)
Current engine load
(display field 3) less than
specified engine load
(display field 2) Duty cycle (display field 4)
close to 99%
Wastegate bypass regulator valve
-N75- malfunctioning Wiring to wastegate bypass
regulator valve -N75-
malfunctioning Wastegate in turbocharger stuck
in open position Leak between turbocharger and
intake manifold Turbocharger malfunctioning
Charge air
pressure too
high
1)
Measured value above 1.47
bar (21.3 psi) (vehicles with
manual transmission)
Measured value above 1.40
bar (20.3 psi) (vehicles with
automatic transmission)
Current engine load
(display field 3) higher
than specified engine load
(display field 2) Duty cycle (display field 4)
close to 0%
Vacuum diaphragm for wastegate
malfunctioning Hoses to vacuum diaphragm (for
wastegate) over wastegate
bypass regulator valve -N75-
leaking Vacuum diaphragm wastegate in
turbocharger stuck in closed
position
1) If charge air pressure is too high, the fuel supply is shut off to protect the engine. The engine misfires at high engine
speeds.
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21-14

Charge pressure leak test with VAG
1687


Intake system, checking for leaks using VAG
1687 Diagnostic Tool
Diagnostic trouble codes (DTCs) related to fuel
trim, charge pressure or mass air flow (MAF)
may be caused by:

Leaking (worn/torn) intake hoses during charge
conditions
Incorrectly torqued or improperly placed clamps
on intake hoses etc. causing leaks during
charge conditions

Check the charge air pressure system using the VAG 1687 Charge air
system tester.
Special tool VAG 1687 Charge air system tester preliminary set-up

- Back off pressure regulator knob -2- of VAG 1687 fully to protect gauge
when shop air supply is applied to assembly.
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The shop air supply line will later be attached to the inlet of VAG 1687. - Close valve -3- before gauge.
- Close valve -4- after gauge.
- Remove female fitting from tester (arrow) and install an appropriate
"male" air fitting that will connect to your shop air supply line (
WARNING!).
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21-15

WARNING!

Use only approved air fittings to adapt shop
air supply line to VAG 1687 tester.

Special tool VAG 1687/1 pressure adapter,
installing (1.8L Turbo)

- Separate intake hose from Mass Air Flow (MAF)
sensor assembly.

Special tool VAG 1687/1 pressure adapter, installing (2.7L BiTurbo)
Repair Manual, Maintenance; Air cleaner housing, cleaning; Air cleaner element, replacing
- Insert VAG 1687/1 pressure adapter in intake hose -black arrow- using
existing clamp (as shown).
- Remove crankcase ventilation tube from intake hose at -white arrow-.
- Remove upper air cleaner housing and hoses to intake manifold as
necessary

- Insert VAG 1687/1 pressure adapter in intake hose -white arrow- using
existing clamp (as shown).
- Disconnect engine crankcase ventilation hose from intake manifold -
black arrow-.
-
Plug intake manifold fitting (for crankcase ventilation hose) with
appropriate hose and metal plug using clamps supplied with VAG
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1687/1 special tool kit.
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