12 51 100 Replacing wiring harness section for ignition coil (N54, N54T)

WARNING: This page is about a different car, the 2010 BMW 135i, 2009 BMW 135i, and 2008 BMW 135i. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT: Aluminum screws/bolts must be replaced each time they are released.
Aluminum screws/bolts are permitted with and without color coding (blue).
For reliable identification:
Jointing torque and angle of rotation must be observed without fail (risk of damage).

IMPORTANT: Read and comply with notes on protection against electrostatic damage (ESD protection). See 61 35... NOTES ON ESD PROTECTION (ELECTRO STATIC DISCHARGE) .

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 acoustic cover . See 11 00 REMOVING AND INSTALLING/REPLACING IGNITION COIL COVER (N54, N54T) .
Remove intake duct . See 13 REMOVING INTAKE 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.

Unlock control unit (2) and raise approx. 5 cm.

Fig 2: Identifying Plug And Control Unit

Courtesy of BMW OF NORTH AMERICA, INC.

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

Fig 3: Pressing Locking Tab

Courtesy of BMW OF NORTH AMERICA, INC.

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

Fig 4: Pressing Locking Tab

Courtesy of BMW OF NORTH AMERICA, INC.

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

Fig 5: Pressing Locking Tab

Courtesy of BMW OF NORTH AMERICA, INC.

Release screws and remove cable duct (1).

Installation:

Replace aluminum screws.

Tightening torque 12 52 2AZ, see 12 52 PLUG CONNECTIONS, TERMINALS, LOOSE PARTS .

Fig 6: Locating Screws And Cable Duct

Courtesy of BMW OF NORTH AMERICA, INC.

WORK STEP FOR UNLOCKING PLUG CONNECTION

Work step	Note:
Disconnect positive lead from battery positive terminal
Unlock plug connections on ignition coils and disconnect
Unlock plug on injectors and disconnect
Release ground connections
Unlock plug on pressure transducers and disconnect
Unlock plug on both solenoid valves and disconnect
Unlock plug on inlet and exhaust camshaft sensors and disconnect
Unlock plug for high-pressure sensor and disconnect
Unlock plug on oil pressure switch and disconnect
Unlock plug on coolant temperature sensor and disconnect
Remove front underbody protection . See 51 47 490 REMOVING AND INSTALLING/REPLACING FRONT UNDERBODY PROTECTION (CONVERTIBLE) or 51 47 490 REMOVING AND INSTALLING / REPLACING FRONT UNDERBODY PROTECTION (COUPE) .
Unlock plug on electric coolant pump and disconnect
Unlock plug on coolant thermostat and disconnect
Release ground connection on engine next to coolant pump	Tightening torque 12 52 3AZ. Replace screw.

NOTE: Check stored fault messages.
Now clear the fault memory.