1999 AUDI A4 engine

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7 -
Vacuum hose
LDP / throttle actuator control module
Connection in engine compartment4 cylinder engine Fig. 16 cylinder engine Fig. 2
8 -
Cable tie
To mounting of vacuum line on LDP
bracket
9 -
Leak Detection Pump (LDP) -V144 Location: in left rear wheel house behind
wheel well Checking Page 20
-139
Removing and installing Page 20
-162
10 -
3-pin harness connector
Black
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Vehicles with 1.8 ltr. turbo engine
The vacuum line for the LDP -V144 is connected to the Throttle actuator
control module line with a T-piece -arrow-. Fig. 1 Connections to LDP in engine compartment

Vehicles with 2.8 ltr. engine
The vacuum line from the LDP -V144 is connected to the EVAP canister
purge regulator valve with a T-piece -arrow-. Fig. 2 Connections to LDP in engine compartment
1 - to EVAP canister
2 - to LDP -V144
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If; however, the reed contact closes within 10
seconds, there is a leak. Then, the pump
continues to cycle for four more strokes. The
ECM measures the time for each of these four
strokes until the next time the reed contact
closes. In this fashion, the ECM can
differentiate between "fine" and "large" leaks.
Leak detection is automatically triggered,
shortly after each engine start. If there is an
incorrect measurement, a malfunction is stored
in DTC memory.
A warning will appear on the instrument panel if
the malfunction has occurred during two
successive drives. Also, leak detection can also
be activated using the VAG1551 Scan Tool
Page 20
-139
.
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Note:
Observe the cover flange installation instructions.

Front wheel drive Page 20
-44


All wheel drive Page 20
-97
.

- Visually inspect all fuel tank system line and
hose connections and replace any leaking lines,
for example:


Line from EVAP canister to EVAP canister
purge regulator valve in engine
compartment.

Lines from EVAP canister to the LDP (under
left wheel house liner).

Line from the fuel tank to the EVAP canister
(under the cover for the EVAP canister).

Lines of the tank ventilation system (under
right wheel house liner).

Fuel lines to the engine.

Note:
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Checking LDP via Read Measuring Value
Block (vehicles with mechanical throttle
control)

Note:

Always replace O-rings, sealing rings and
gaskets.
Radiator fan must not come on during the
test!

Troubleshooting requirements
DTC memory checked and no DTCs stored
All electrical consumers switched OFF
A/C switched OFF
Intake Air Temperature lower than 90 C
Display group 004, channel 4.

Engine Coolant Temperature less than 95
C Display group 004, channel 3.

Throttle angle less than 10 % Display
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Note:
In the following description the performance of the On Board Diagnostic
(OBD) procedure the VAG1551 Scan Tool (ST) is used. When using
Vehicle Diagnostics Test and Information System VAS5051, use the
operating instructions. - Connect VAS5051 with diagnostic cable VAS5051/1 or VAG1551 Scan
Tool (ST) with adapter cable VAG1551/3B.
- Start engine and let idle.
On Board Dia
gnostic
HELP
1 - Rapid data transfer 1
)
2 - Blink code 1
)

Indicated on display: 1) Appears alternately
- Switch ignition on.
- Press button 1 to select "Rapid data transfer".
Rapid data transfer
HELP
Enter address word XX

Display will appear as shown
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- Press 0 and 1 buttons to select Address word
01: "Engine electronics".

- Press Q button to enter input.

-
Press button.Rapid data transfer
HELP
Select Function XX

Display will appear as shown
- Press 0 and 8 buttons to select Function 08: "Read measuring value
block"
- Press Q button to enter input.
Read measurin
g value block
Enter displa
y group number XXX

Display will appear as shown
- Press 0, 7 and 1 buttons to select "display group 71".
- Press Q button to enter input.
Read measuring value block Reed closed
break
Test OFF

Display will appear as shown
Note:
Condition for continuing test is "Reed closed" on the display.The display does not always show "Abort".If the display: "reed open" appears: Briefly open the filler cap to
reduce pressure - this will close the reed contact. Continue checking
as follows:
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Rapid data transfer
HELP
Enter address word XX

Indicated on display:
- Enter "01" for address word "Engine electronics" and confirm input by
pressing Q button.
-
Press button.
Rapid data transfer
HELP
Select function XX

Indicated on display:
- Enter "03" for function "Output Diagnostic Test Mode (DTM)."
Rapid data transfer
Q
03-Output Diagnostic Test Mode

Indicated on display:
- Confirm input by pressing Q-button.
Output Diagnostic Test Mode EVAP Purge Regulator Valve
-N80

Indicated on display (EVAP canister purge regulator valve -N80)
-
Press button until following display is shown:
Output Diagnostic Test Mode Leak Detection Pump

Indicated on display:
Note:
You can hear the leak detection pump run at the left rear wheel housing
when it is working. This will be difficult to hear. Make sure to be as close
to LDP as possible and to eliminate as much surrounding noise as
possible. The leak detection pump is activated for about 1 minute.
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