Procedure that must be performed before opening the high-pressure fuel injection system. Pay close attention!

WARNING: This page is about a different car, the 2009 Audi A4, 2008 Audi A4, 2007 Audi A4, 2006 Audi A4, and 2005 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.

The fuel injection system is separated into a high-pressure section (max. approx. 110 bar) and a low-pressure section (approx. 6 bar).
Before opening the high-pressure section - e.g. removing high-pressure pump, fuel rail, fuel injectors, the motor for intake manifold runner control valve or any other component or fuel line that is located in the high-pressure section of the fuel injection system - the fuel pressure in the high-pressure section must be relieved to a residual pressure of approx. 8 bar. The procedure for this is as follows.

Special tools, testers and auxiliary items required

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

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Vehicle Diagnostic, Testing and Information System VAS 505 with Diagnostic Cable VAS 5051/5A (VAS 5051 B version shown as example only)

Work procedure

Start engine and run at idle speed.

Fig 2: Connecting Data Link Connector (DLC)

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Connect Vehicle Diagnosis, Testing and Information System VAS 5051 with Diagnostic Cable VAS 5051/5A.

Fig 3: Diagnostic System VAS 5051: Display

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Display on VAS 5051 :

Click on Vehicle Self-Diagnosis button.

Fig 4: Diagnostic System VAS 5051: Display

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Display on VAS 5051 :

In selection - 1 - , press vehicle system "01 - Engine electronics".
Wait until next display appears.

Fig 5: VAS 5051 Tester Displaying Control Module Identification And Coding

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Display on VAS 5051 :

1 - Control module identification of engine control module (ECM)

Click on → button.

Fig 6: Diagnostic System VAS 5051: Display

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Display on VAS 5051 :

1 - Selection of diagnostic functions

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

Fig 7: Diagnostic System VAS 5051: Display

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Display on VAS 5051 :

Select "140" in button field - 2 - for "display group 140" and confirm input by pressing Q button.

Fig 8: Diagnostic System VAS 5051: Display

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Courtesy of VOLKSWAGEN UNITED STATES, INC.

Display on VAS 5051 :

Example:

42%
39.76 bar
40.63 bar
Inactive

Fig 9: Diagnostic System VAS 5051: Display - Display Fields

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Activate basic setting by pressing button A.

Display on VAS 5051 :

Example:

0%
0 bar
5.46 bar
Lower

The fuel rail will continue to be filled with fuel, but it will no longer be under high pressure.

Now components or lines can be opened. A clean rag must be placed around the connection points. Escaping fuel must be absorbed.

In operating mode "Guided Fault-Finding" , generate readiness code for engine control module (ECM).