12 14 600 Removing/Replacing Knock Sensors (N54, N53)

Special tools required:

13 5 281
13 5 282. See FUEL SUPPLY SYSTEM -- SPECIAL TOOLS -- TWIN TURBO .
32 1 270. See STEERING AND WHEEL ALIGNMENT - SPECIAL TOOLS .

WARNING:

Disconnect battery negative terminal (risk of fire due to short-circuiting on removal).

Electric fuel pump starts up automatically each time door is opened!

Carry out installation work on fuel system only with coolant temperature below 40°C.

IMPORTANT:

Adhere to conditions of absolute cleanliness when working on the high-pressure fuel system.

Introduced contaminants can cause malfunctions in the system!

Do not allow any dirt particles or foreign bodies to get into the system.
Remove all traces of dirt before removing pipes or individual components.
Use only fluff-free cloths.
Seal all fuel system openings with protective caps or plugs.

IMPORTANT:

Aluminum screws/bolts must be replaced each time they are released .

The end faces of aluminum screws/bolts are painted blue for the purposes of reliable identification.

Jointing torque and angle of rotation must be observed without fail (risk of damage) .

Necessary preliminary tasks:

Read out fault memory of DME control unit
Switch off ignition
Remove intake air manifold

NOTE: Illustration shows N54.

Recycling:

Fuel escapes when fuel lines are detached.

Catch and dispose of escaping fuel.

Observe country-specific waste-disposal regulations.

Unlock plug (1) and remove.

Unlock and detach fuel line (2).

Catch and dispose of escaping fuel.

Fig 1: Identifying Fuel Line & Plug

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Seal fuel lines with special tools 13 5 281 and 13 5 282.

Fig 2: Identifying Special Tools (13 5 281 & 13 5 282)

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Unscrew nut (1).

Seal fuel line connection of high-pressure pump with a matching plug from special tool kit 32 1 270.

Release screw (2).

Installation:

Replace aluminum screw.

Remove feed line (3).

Fig 3: Identifying Fuel Line Connection

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Seal feed line with matching plug from special tool kit 32 1 270.

Fig 4: Identifying Special Tool Kit (32 1 270)

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Unlock plug (1) and remove.

Fig 5: Identifying Unlock Plug

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Release screws on both knock sensors (1) and remove knock sensors (1).

Installation:

Replace aluminum screws.
Tightening torque 12 14 1AZ, see ENGINE ELECTRICAL SYSTEM -- TORQUE SPECIFICATIONS -- TWIN TURBO .

Fig 6: Locating Aluminum Screws
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Installation:

Clean contact surface of knock sensors on engine block.

Fig 7: Locating Surface Of Knock Sensors On Engine Block

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Installation:

Pre-install feed line (3).

In so doing, tighten screw connection hand-tight only (it must still be possible to move the line at the holder).

IMPORTANT: Sequence of screw connection must be observed!

Tighten nut (1). Tightening torque 13 53 6AZ. See FUEL SYSTEM -- TIGHTENING TORQUE -- TWIN TURBO .
Tighten screw (2). Replace aluminum screw. Tightening torque 13 53 9AZ. See FUEL SYSTEM -- TIGHTENING TORQUE -- TWIN TURBO .

Fig 8: Identifying Feed Line & Screw
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NOTE:

Check stored fault messages.

Now clear the fault memory.