Necessary preliminary tasks:

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Read out fault memory of control unit of Digital Motor Electronics (DME).
Switch off ignition.
Remove design cover.
Unlock hose on tank venting valve and disconnect.

NOTE: Solenoid valve (1) controls adjusting unit on inlet side.
Solenoid valve (2) controls adjusting unit on exhaust side.

Fig 1: Locating Solenoid Valves

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Unlock plug of solenoid valves (1 and 2) and disconnect.

Release screws and remove holder (3). Pull out solenoid valves (1 and 2).

Installation:

Check holder (3) for deformation; replace if necessary.

Installation:

Clean sealing faces (1) on cylinder head.

Fig 2: Cleaning Sealing Faces

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Installation:

Replace O-rings (1 and 2) on solenoid valve (3) and lubricate.

Fig 3: Identifying O-Rings On Solenoid Valve

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Installation:

Press in solenoid valve as far as it will go.

Fig 4: Pressing In Solenoid Valve

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Make sure holders are in correct installation positions.

Install and tighten down screws.

Now clear the fault memory.