display AUDI A4 1998 B5 / 1.G EVAP Workshop Manual

20-138

- Visually inspect the fuel supply system
components:


Fuel tank

EVAP canister

LDP

EVAP canister purge regulator valve -N80

Note:
At times, the above components cannot be
effectively leak tested using a leak detection
spray, either because of component location or
function. In such cases, clamp off the lines to the
component involved and perform a leak check. If
the leak is no longer displayed, the clamped off
component is faulty. If the LDP is clamped off
and there is still a leak displayed, the LDP is
faulty.

- Check EVAP canister purge regulator valve -
N80

Repair Manual, Fuel Injection & Ignition,
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20-140

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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20-141


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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20-142

- 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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20-143

- Press 0 and 4 buttons to select Function 04:
"Basic Setting". System in basic adjustment 71 Reed closed

Test ON

Display will appear as shown
The EVAP canister valve is opened to allow pressure relief in the
system. Then the LDP -V144 will be triggered. The total procedure lasts approx. 60 seconds.
-
Press button .
System in Basic Adjustment 71 Reed open
Syst.Test
Test ON

Display will appear as shown
The system makes a test, the LDP -V144 starts running and shuts off
when the pump running time reaches a pre-determined time-out. The total procedure lasts approx. 60 seconds.
System in Basic Adjustment 71 Reed open
Measurement
Test >ON

Display will appear as shown
Measurement phase begins. The LDP -V144 is switched off and the
ECM checks whether the reed contact has closed within 10 seconds.
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20-144
If NO System in Basic Adjustment 71 Reed open
Messg. END
Syst.OK

Display will appear as shown
If contact does not close within 10 seconds
The system is sealed and the measurement is ended.
-
Press button.
- Press 0 and 6 buttons to select Function 06: "End output"
- Press Q button to enter input.
The LDP -V144 performs 4 pump strokes. The ECM compares the
time it takes to carry out the pump strokes and the time until the reed
contact closes again.
System in Basic Adjustment 71 Reed clos fine leak Messg. ENDSyst.n OK

Display will appear as shown
The system has recognized a fine leak ( greater than 1 mm).
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20-145

System in Basic Adjustment 71 Reed clos lr
g leak Mess
g. ENDS
yst.not oK

Display will appear as shown
If system has recognized a fine or large leak
The Leak detection system has recognized a large leak.
-
Press button.
- Check tank system and tank ventilation system for leaks Page 20
-
136
.
- Perform tank leak diagnosis again.
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20-146

Checking LDP via output DTM (vehicles with
electronic throttle control)

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.
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".
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20-147

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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20-156

Checking output wiring (vehicles with
electronic throttle control)

- Connect voltage tester VAG1527B as follows:Electrical connector terminal
Specification
2 Battery Positive
- Initiate Diagnostic Test Mode (DTM) Page 20
-146
.
-
Press button until following display is shown:
Output Diagnostic Test Mode LDP leak test

Indicated on display:
If LED does not blink:
LED must blink
- Switch ignition off.
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