AUDI A8 1999 D2 / 1.G AEB Engine Turbocharger Boost Control And Checking

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Turbocharger boost controls,
checking

Boost pressure regulation, checking


- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with engine
running at idle) Page 01
-7 .
Rapid data transfer
HELP
Select function XX

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

Indicated on display
- Press buttons -1-, -1- and -4- to input display group number 114, and
press -Q- button to confirm input.
Read Measuring Value Block 114 1 2 3 4

Indicated on display (1-4 = display fields)
WARNING!
A second technician is required to operate the VAG 1551 scan tool
during the road test. - Road test car at wide open throttle at 4000 RPM.
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- Compare display with specified value for
wastegate bypass regulator valve duty cycle in
display field 4:

Specified value: 5-95 %
If displayed value is OK:

- Change engine RPM until duty cycle is within
specified value.

- Compare display with specified value for
corrected specific engine load in display field 2:

Specified value: 3.00-8.00 ms

- Compare display with specified value for actual
engine load in display field 3:

Specified value: must be same as corrected
specified engine load in display field 2 (with
tolerance of 0.50 ms)
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Display fields

1 2 3 4
Display group 114: Boost pressure regulation
Display xx.xx ms xx.xx ms xx.xx ms xx %
Indicates Specified
engine load Corrected specified
engine load Actual engine load Duty cycle of wastegate
bypass regulator valve
Range --- --- --- 0-99 %
Specified
value --- 3.00-8.00 ms Same as corrected specific engine load in
display field 2 (tolerance 0.50 ms)
5-99 %
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If the actual engine load is not within the
tolerance, possible malfunctions are:

Wastegate bypass regulator valve electrical
malfunction
Hoses for wastegate bypass regulator valve
disconnected or blocked
Wastegate bypass regulator valve -N75-
blocked
Air leaks between turbocharger and intake
manifold
Wastegate bypass regulator valve mechanical
controls sticking (linkage, shaft)
Turbocharger faulty (turbine blocked by foreign
object)
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Wastegate bypass regulator valve,
checking


Function

With power off, the long connector is closed.
Both short connecters are inter-connected.
When triggered, the connection between the
long and both short connectors is opened.

Check for leaks

- Remove wastegate bypass regulator valve (
component location, page Page 24
-1 )

- Re-connect removed wastegate bypass
regulator valve to wiring harness.

- Start output Diagnostic Test Mode (DTM) and
advance through test program to select
wastegate bypass regulator valve -N75- Page
01
-42


- Blow into long connector during DTM to check
whether valve opens properly.
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If necessary:

- Replace wastegate bypass regulator valve -N75-
.
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Checking wastegate bypass regulator valve -
N75-

- Disconnect harness connector from valve -
N75-.

If resistance is not OK: - Connect multimeter US 1119 (Fluke 83 or equivalent) to check
resistance between terminals of valve -N75-.

Specified value: 25-35 - Replace valve.
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Check voltage supply for wastegate bypass
regulator valve -N75-

Note:
Voltage supply for the wastegate bypass
regulator valve is provided by the fuel pump
relay.

Fuse for -N75- OK

- Disconnect harness connector from valve.

If LED does not light:
If wiring is OK: - Connect VAG 1527B LED test light between harness connector
terminal 1 and engine Ground.
- Operate starter motor.
LED test light must light up
- Check wiring for open circuit between terminal 1 to and fuse, according
to wiring diagram. Repair if necessary.
- Check fuel pump relay Page 24
-81
.
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Signal for wastegate bypass regulator valve,
checking

- Disconnect harness connector for valve -N75 .

If LED test light does not blink, or stays on continuously: - Connect VAG 1527B LED voltage tester between connector terminals
1 (B+) and 2.
- Start output Diagnostic Test Mode (DTM) and advance through test
program to select wastegate bypass regulator valve -N75- Page 01
-
42

LED test light must blink
- Connect VAG 1598/22 test box to ECM harness connector Page 01
-
56
.

If wiring is OK: - Check wiring for open circuit or short circuit to B+ between connector
terminal 2 and ECM/test box socket 64. Repair if necessary.
- Replace Motronic ECM -J220- Page 01
-57
.
- Carry out adaptation of throttle valve control module to ECM Page
24
-119
.
- Check readiness code Page 01
-59
. If Diagnostic Trouble Code
(DTC) memory has been erased, or ECM was disconnected, generate
new readiness code Page 01
-62
.
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Barometric Pressure (BARO) sensor,
checking


Note:
The signal from Barometric Pressure (BARO)
sensor -F96- influences:

Boost pressure limit
Mixture composition at engine start-up

Required special tools and test equipment
VAG 1551 or VAG 1552 Scan Tool (ST) with
VAG 1551/3 adapter cable
VAG 1598/22 test box
Multimeter US 1119 (Fluke 83 or equivalent)
VW 1594 connector test kit
Wiring diagrams

Checking

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