12 14 600 Removing/Replacing Knock Sensors (N51, N52, N52K)
Aluminum-magnesium materials .
No steel screws/bolts may be used due to the threat of electrochemical corrosion.
A magnesium crankcase requires aluminum screws/bolts exclusively.
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:
Aluminum screws/bolts are not magnetic .
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
- Clamp off battery negative lead . See 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD (CONVERTIBLE) or 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD (COUPE) .
- Remove intake air manifold . See 11 61 050 REMOVING AND INSTALLING INTAKE AIR MANIFOLD (N51) .
Unlock plug (1) and remove.
Release screws on both knock sensors (1) and remove knock sensors (1).
Installation:
Replace aluminum screws .
Tightening torque, see 12 14 1AZ in 12 14 ELECTRONIC SHIFT UNITS OR CONTROL UNITS .
Installation:
Clean support face of knock sensors on engine block.
Check stored fault messages.
Now clear the fault memory.