1996 AUDI TT AEB ATW Engines Turbocharger System Workshop Manual

21-8

Vehicles with manual transmission:

- Accelerate vehicle in 3rd gear at full throttle from
2000 RPM and watch tachometer.

Vehicles with automatic transmission: - At 3000 RPM press memory button "M" on turbocharger tester.
Specification: 1.37-1.47 bar (19.865-21.315 psi)
- Drive with selector lever in range 2.
- Accelerate to 3000 RPM and wait for transmission to shift into 2nd
gear.
- Press accelerator pedal to kickdown position (transmission will not shift
down at this vehicle/engine speed).
- At 4500 RPM, press memory button "M" on turbocharger tester.
Specification: 1.3-1.4 bar (18.85-20.30 psi)
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21-9

Note:
For vehicles with automatic transmission the
charge air pressure test may not always provide
a definitive reading of proper charge air pressure
regulation. If pressure readings are at the lower
end of the specified range, measure charge air
pressure control via load signal Page 21
-10
.

All vehicles:
If measured value is above or below specification
Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel
Injection & Ignition, Repair Group 24.

Note:
If no charge air exists and a rumbling sound is
heard from the engine compartment, the causes
are as follows:

Charge pressure bypass valve
malfunctioning.
Vacuum line to charge pressure bypass valve
leaking or disconnected.
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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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