P0305 means the ECU counted enough missed combustion events on cylinder 5 (typically over 2% of firings in a 200-rev window) to trip the misfire monitor. Expect rough running and a flashing CEL under load.
DTC/P0305·BMW
P0305 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
High SeverityNot safe to driveBMW
P0305 on a BMW means the ECU counted enough missed combustion events on cylinder 5 (typically over 2% of firings in a 200-rev window) to trip the misfire monitor. Expect rough running and a flashing CEL under load.
Repair cost on BMW€63 - €3780
What does P0305 mean on a BMW?
BMW 3-Series E90/E92 (N54, N55)
2007-2013N54 and N55 inline-sixes chew through Bosch coils and NGK index plugs. N54 injectors were covered by an extended warranty (10 years/120,000 miles (190,000 km) in the US) for exactly this failure mode.
What causes P0305 on a BMW?
Beyond the generic causes listed on the main P0305 page, these are the BMW-specific patterns we see most often:
BMW 3-Series E90/E92 (N54, N55)Bosch coil pack failure (replace as a matched set of 6)
BMW 3-Series E90/E92 (N54, N55)N54 piezo injector failure causing lean misfire (recall/extended warranty items)
BMW 3-Series E90/E92 (N54, N55)HPFP weakness dropping rail pressure under load on N54
How to diagnose P0305 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0305:
- Read all stored and pending codes. Note fuel trims and any lean/rich codes (P0171, P0174) that could point at a vacuum or injector issue.
- Pull the coil and plug from cylinder 5. Fouled electrode, cracked insulator, or oil in the plug well tells you a lot before you swap anything.
- Swap the cylinder 5 coil with a neighbouring cylinder, clear codes, and drive. If the code moves (e.g. becomes P0303), replace the coil.
- Swap the injector connector or the injector itself with a neighbour if the coil swap didn't move the misfire. A noid light confirms the ECU is pulsing the injector.
- Check live fuel trims and misfire counters with a scan tool. Positive trim on the affected bank points to vacuum leak or weak injector flow.
- Smoke-test the intake if trims are lean. Cracked PCV hoses and split intake boots are common culprits.
- Compression test cylinder 5. More than 15% below the average of the other cylinders points to mechanical trouble. Follow up with a leakdown to isolate valves vs rings.
- After repair, clear codes and complete a misfire monitor drive cycle before declaring victory.
How much does P0305 cost to fix on a BMW? (EUR)
Estimated repair costs on a BMW (BMW parts and labour typically run 40% above the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0305 on BMW
These codes commonly cluster with P0305 on BMW vehicles:
FAQ: P0305 on BMW
Can I swap the cylinder 5 coil with another cylinder to test it?
Yes, and it's the fastest free test you can do. Move the cylinder 5 coil to cylinder 1 or 3, clear the code, and drive. If P0301 or P0303 pops, the coil is bad. If P0305 comes back, the coil is fine and you're looking at plug, injector, or mechanical.
Will driving with P0305 kill my catalytic converter?
Yes, and quickly. A flashing CEL means raw fuel is hitting a red-hot cat. A sustained misfire can destroy a converter in a few hundred kilometres, turning an €80 coil job into a €600-€1500 cat replacement.
Why does cylinder 5 fail more often than other cylinders?
On most transverse V6s and longitudinal V8s, cylinder 5 sits at the rear of the head where heat soak from the firewall or exhaust is worst. Coils cook faster there. On inline sixes it's simply the second-hottest position. It's not random - rear cylinders live a harder life.
The misfire only happens when the engine is cold. What causes that?
Cold-only misfires usually point to a coil breaking down when secondary resistance is highest, a cracked plug insulator arcing to ground, or an injector that's slow to open cold. Warm-only misfires more often mean a heat-sensitive coil or a compression issue that seals up as the head expands.
I replaced the plug and coil but P0305 came back. What next?
Move to the fuel and vacuum side. Check injector resistance (typically 12-16 ohms on port injection), listen with a mechanic's stethoscope for the click, and smoke-test the intake. If all that's clean, run a compression and leakdown test before spending more on parts.
Looking for the full P0305 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0305 guideSkanyx · BMW
Diagnosing P0305 on your BMW?
Your car logged {code}. Skanyx reads it on any standard Bluetooth OBD2 adapter, tells you whether it is safe to keep driving, and shows the {costRange} repair range so you know the number before a shop quotes you.
Download Skanyx