12 51 001 Replacing wiring harness section for engine (N54, N54T)

Necessary preliminary tasks: 

• Read out fault memory of DME control unit
• Switch off ignition
• Disconnect battery negative lead  . See 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD .
• Remove intake air manifold  . See 11 61 050 REMOVING AND INSTALLING INTAKE AIR MANIFOLD (N54, N54T) .
• Remove charge air duct  . See 11 61 368 REMOVING AND INSTALLING/REPLACING REAR LEFT CHARGE-AIR DUCT (N54, N54T) .

Unlock fasteners (1) from below and slide upwards approx. 10 mm.

Unlock locks (2) in direction of arrow.

Remove cover (3).

Fig 1: Unlocking Locks

Courtesy of BMW OF NORTH AMERICA, INC.

Unlock plug (1) and remove.

Release grommet (2) from electronics box.

Installation: 

Make sure grommet (2) is correctly seated in housing (watertightness).

Raise control unit (3) slightly.

Fig 2: Identifying Plug, Grommet And Control Unit

Courtesy of BMW OF NORTH AMERICA, INC.

Unlock plugs (1) using slide in direction of arrow and disconnect.

Fig 3: Unlocking Plugs

Courtesy of BMW OF NORTH AMERICA, INC.

Short plug:

Unlock slide (2) in bore holes (1) and pull out of housing.

Unlock tab (3), pull contact carrier (4) in direction of arrow out of housing.

Fig 4: Pulling Contact Carrier

Courtesy of BMW OF NORTH AMERICA, INC.

Long plug:

Press locking tab (1) in direction of arrow and pull contact carrier (2) out of housing.

Unlock and disconnect all plug connections of engine wiring harness section in electronics box.

Fig 5: Pressing Locking Tab

Courtesy of BMW OF NORTH AMERICA, INC.