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BMW P0300 and misfire codes (P0301–P0306, 29CC–29D2)
One or more cylinders aren't firing properly. On BMWs: ignition coils and spark plugs first, then injectors (N54 and N63 especially).
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Codes on this page
| Code | Definition | Source |
|---|---|---|
| P0300 | Random/multiple cylinder misfire detected | Generic OBD-II |
| P0301–P0306 | Cylinder 1–6 misfire detected | Generic OBD-II |
| 29CC | Misfirings, several cylinders (E-series sixes) | BMW SI B07 03 14 |
| 29CD–29D2 | Misfirings, cylinder 1–6 | BMW SI B07 03 14 |
| 2B16–2B1D, 2B22 | Engine misfires, individual cylinders / several cylinders (N63 V8, E71 X6) | SI B01 02 19 (PDF) |
P-codes are the generic OBD-II codes any reader shows. Six-character and four-character hex codes are BMW's own, read with a BMW-capable scanner; the wording is BMW's, from the source shown.
What it means
The engine computer counts misfires from small changes in crankshaft speed. A specific cylinder code (P0301–P0306, or BMW 29CD–29D2 on the sixes) names the cylinder; P0300 or 29CC means several or random cylinders. A flashing check engine light means the misfire is bad enough to damage the catalytic converter.
Can I keep driving?
Steady light: gently, to a shop. Flashing: stop. The EPA advises that a blinking check engine light means a severe problem like a misfire: minimise driving, avoid high speed and heavy loads, and get it repaired quickly. Unburned fuel can overheat the catalytic converter.
Usual causes on BMWs
| Cause | Cars most affected | What you notice | Evidence | Repair prices (national average) |
|---|---|---|---|---|
| Ignition coil or spark plug | All gasoline engines | One cylinder code that moves when you swap that coil with another cylinder. BMW also ran a service action on some 2023 G05 X5 and G07 X7 ignition coils with excess silicone. | SI B12 01 24 (PDF) | N55 ignition coils (all six) Indie $355–$789 Dealer $1,064–$1,299 |
| Fuel injectors (direct injection) | N54 (piezo injectors), N63 and S63 | Cold-start rough running with several misfire codes. BMW extended injector coverage on N54, N54T, N63, N63T and S63 cars and ran a voluntary emissions recall on N54 injectors. | SI B13 04 09 (PDF) SI B13 14 10 (PDF) SI B01 02 15 (PDF) SI B01 17 15 (PDF) SI B01 01 15 (PDF) SI B01 05 18 (PDF) SI B01 03 15 (PDF) | — |
| Low fuel pressure | N54 above all | Misfires stored together with high-pressure fuel codes 29DC/29F2. | SI B12 55 06 (PDF) | N54 high-pressure fuel pump (HPFP) replacement Indie $745–$1,586 Dealer $2,086–$2,523 |
| Engine computer or software | N20, N26, N55 (injector electrical faults); N63T (erroneous misfires at constant highway speed) | BMW bulletins say not to replace injectors for some injector electrical faults (an internal DME fault), and fixed false N63T misfire codes with software. | SI B12 38 14 (PDF) SI B12 10 16 (PDF) | — |
| Vacuum leaks and carbon build-up | Direct-injection engines | Rough idle with lean codes; the misfire codes are a side effect. | — | N55 valve cover / valve cover gasket (PCV) Indie $1,225–$1,547 Dealer $2,017–$2,557 Indie owners paid $930–$1,625 Dealer owners paid $1,450–$2,076 |
A bulletin isn't a recall and doesn't mean your car has the problem; open it for the exact models and build dates. Estimates are national averages built from BMW warranty labor time, regional shop rates and parts prices; open a repair for your ZIP. "Owners paid" is the middle half of sourced prices, shown where we have at least 3.
What to do
- Note which cylinder(s) the code names.
- Swap that cylinder's coil with a neighbour and recheck; if the misfire moves, it's the coil.
- Check spark plug age against your maintenance schedule.
- On N54, N63 and S63 cars, ask about injector warranty extensions before paying.
Warnings it can bring up
Other BMW bulletins that mention it
- SI B12 09 20 I01 rex: misfires at high altitudes using winter-blend fuel I01 · Sep 2020
- SI B13 04 09 N54 - Diagnosis of Cold Start Rough Running with Misfire Faults E60, E61, E82, E88, E89 and others · Feb 2013
- SI B13 04 09 N54 Engine: Diagnosis of Cold Start Rough Running with Misfire Faults E60, E61, E71, E82, E88 and others · Mar 2013
- SI B13 05 14 N20 and N26 Misfire and Drivability Diagnosis Hints E60, E84, E89, E90, E92 and others · Oct 2014
- SI B13 07 12 N63 and S63 Engine: High-pressure Fuel Injector Replacement Procedures E60, E70, E71, E72, E82 and others · Dec 2014
- SI B13 07 12 N63 and S63 Engine: High-pressure Fuel Injector Replacement Procedures E60, E70, E71, E72, E82 and others · May 2014
- SI B13 07 12 N63 and S63 Engine: High-pressure Fuel Injector Replacement Procedures E60, E70, E71, E72, F01 and others · Apr 2014
- SI B13 07 12 N63 and S63 Engine: High-pressure Fuel Injector Replacement Procedures E60, E70, E71, E72, E82 and others · Oct 2013
38 of the BMW bulletins we hold mention it in their text; these are the closest matches.
Sources
- OBD-Codes.com: P0300 definition
- US EPA: What to do with the check engine light (EPA420-F-00-041)
- BMW SI B07 03 14: Diagnosing stored fault codes to help avoid repeat repair visits (NHTSA)
- NHTSA: BMW technical service bulletins and recalls by VIN
Bulletins are cited in the tables above. Explanations are ours; where a source is an owner report rather than BMW, it is labelled as one.