Diagnostic leak test, performing

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Special tools, testers and auxiliary items required

Fig 1: Identifying Vehicle Diagnosis, Testing And Information System VAS 5051B

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Vehicle Diagnostic, Testing and Information System VAS 5051 with diagnostic cable VAS 5051/5A (VAS 5051 B version shown as example only)

Observe safety precautions → Safety precautions when working on fuel supply system .

Observe rules for cleanliness → Rules for cleanliness .

NOTE:

Secure all hose connections using hose clamps appropriate for the model type .
Replace O-rings and gaskets when performing repair work.

Test conditions

Parking brake is applied.
Vehicles with manual transmission: Shift lever in neutral.
Vehicles with automatic transmission: Selector lever in position "P" or "N".
Engine running at idle speed or with brakes actuated and accelerator fully depressed (elevated engine RPM).

Electrical consumers switched off (Radiator fan must not run during test).
Air conditioning system switched off.

Fig 2: Connecting Data Link Connector (DLC)

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Vehicle Diagnostic, Testing and Information System VAS 5051 connected, On-board diagnostics and Data Link Connector DLC "01 Engine electronics" selected.
No DTCs in DTC memory.
Intake air temperature less than 90 ° C → Measuring value block 004, display field 4.
Coolant temperature less than 95 ° C → Measuring value block 004, display field 3.

Throttle valve angle less than 10 ° C → Measuring value block 003, display field 3.

Test sequence

Fig 3: Diagnostic System VAS 5051: Display

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Display on VAS 5051 :

In selection - 1 - , click on diagnostic function "04 - Basic Setting".

Fig 4: Diagnostic System VAS 5051: Display

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Display on VAS 5051 :

1 - Enter display group

Select function "071" in button field - 2 - for "display group number 071" and press Q to confirm input.

Fig 5: Diagnostic System VAS 5051: Display - Display Fields

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Display on VAS 5051 :

Check reading in display field - 1 -.

Specification: "Reed closed."

NOTE:

If "Reed closed" is displayed, continue test.
If the reading on the display shows "Reed open" : Briefly open the cap of the fuel tank to relieve pressure - thereby the reed contact will close again.

Activate basic setting by pressing Activate button - A -.
Check reading in display field - 4 -.

Specification: "Test ON"

The system test takes several minutes.

Check reading in display field - 4 -.

Specification: "Syst.O.K."

The system is sealed, the test is ended.

End function "04 - Basic setting" by pressing ← button.

Fault indication

If a malfunction was recognized during the system test, the malfunction is indicated afterward.

Fig 6: Diagnostic System VAS 5051: Display - Display Fields

Courtesy of VOLKSWAGEN UNITED STATES, INC.

On VAS 5051 display in display field - 4- - :

In case of malfunction: Syst. n.O.K.

Check readings of diagnosis in display field - 2 -.

"Small leak" or "Large leak"

End function "04 - Basic setting" by pressing ← button.

If the system has recognized a small or large leak:

Check fuel supply and tank ventilation systems for leaks → Fuel supply and tank ventilation systems, checking for leaks .
Afterwards, perform the leak diagnosis again.