What code P0306 means
Per-cylinder misfire on cylinder 6. The last cylinder of an inline-6 (N52, N54, N55, B58) and the front or rear of a V6.
How to read a per-cylinder misfire code
Per-cylinder misfire codes identify the cylinder. P0300 means random or multiple cylinders; P0301 through P0308 (and on some engines higher) tell you which one. Read the misfire counter histogram before changing parts.
- Read the freeze frame.
Engine speed, load, coolant temperature and fuel trim at the moment the misfire was counted. Cold-engine misfires that disappear when warm are usually ignition. Hot-engine misfires are usually fuel or compression.
- Read the misfire counter histogram.
Beemuu’s Logging tab can capture the per-cylinder misfire counter over time. A single cylinder with a sharply higher count points at that cylinder.
- Swap-test the ignition coil.
On engines with known coil failures (N54/N55 in particular), moving a suspect coil to a known-good cylinder is faster than replacing all of them.
- Inspect the injector harness.
BMW injector connectors age. A chafed wire produces intermittent misfires that look like a coil fault.
- Compression-test if everything else passes.
If the same cylinder misfires after a fresh coil, plug and known-good injector, suspect compression. A leak-down test pinpoints rings vs. valves.
Related codes in the same family
A DTC tells you what a control module decided is outside its expected range. It does not automatically identify a failed component. Read freeze frames, compare related codes, and inspect live data before changing parts. Service functions and coding operations are write paths — use a battery maintainer where the procedure requires stable voltage and never perform writes you do not understand.
P0306 questions
What does code P0306 mean?
Cylinder 6 misfire detected.
Is P0306 a BMW-specific code?
No — {code} is a generic SAE J2012 code; it applies to every OBD-II vehicle, not just BMW.
How do I read P0306 with Beemuu?
Connect on K+DCAN or ENET/DoIP, run a vehicle scan, and look up P0306 in the fault list. Beemuu preserves the code, description and freeze frame before you clear anything.
What does the severity mean?
Critical means the code is usually associated with drivability or safety; warn means investigate soon; info means it is a state or condition rather than an outright fault.