P0304 Cylinder 4 is misfiring
190 owner reports and 840 manufacturer filings across 284 model years from Acura, Alfa Romeo, Audi, Chevrolet and others.
Where P0304 shows up
Source: NHTSA manufacturer communications and complaintsShowing the 25 model years where P0304 appears most; it is on file for 284 in total.
A model year appears here because the code is named in its record, not because every one of these vehicles sets it. Counts are mentions in the federal files, not failure rates — nobody publishes the denominator.
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P0304 by make
The same record, one make at a time: the model years, bulletins and owner reports that name P0304 on that maker’s vehicles.
What it gets filed under
When owners report it
miles, typically
Half of the 32 owner reports naming P0304 that carry an odometer reading fall between 56,000 and 87,000 miles. A code that shows up at 30,000 miles is a different proposition from one that shows up at 130,000, and that difference is the single most useful thing in this record.
What owners said
Source: NHTSA complaint databaseOwners’ own words, one per nameplate, scrubbed of anything identifying. These are unverified reports filed with NHTSA — they are what was said, not a finding that it was true.
It had all these codes all of a sudden P0304 P0305 P0306 P0300 P0430 P219B All of these codes are associated with a bulletin on Honda for an extended warranty for 2019 Pilots all makes up to 10yr/150k miles for a fuel injection issue
In June 2019, an authorized FCA dealership diagnosed DTC P0304 (cylinder 4 misfire), identified an ignition-coil boot electrical short, and replaced all four ignition-coil boots under the manufacturer’s 15-year/150,000-mile PZEV emissions…
Diagnostic codes at failure: P0304 (cylinder 4 misfire), P219F (cylinder imbalance), P0014 and P0017 (camshaft/crankshaft timing correlation), P1327 (knock sensor) - internal engine and timing damage consistent with the recalled defect
On October 6, 2026, at 197,216 miles, an O’Reilly scan recorded stored P0304 (cylinder 4 misfire) and P1101 (intake airflow system performance)
Dealer found engine oil below the low mark, no external leaks, DTCs P0302/P0304 (misfires cyl 2 & 4), and all spark plugs worn/fouled
840 manufacturer filings name P0304. Start with what the maker wrote down.
A code names the test that failed, not the part. A bulletin that names it is often a diagnosis someone has already written down — quote its number at the service desk.
Manufacturer filings that name it
Source: NHTSA manufacturer communicationsService bulletins and campaigns whose filed summary names P0304.
- B26-001 Service bulletin2026-09-25 · Engine
- Service Bulletin - Under certain conditions, the cylinder head gasket effectiveness may be reduced which may cause vehicles to experience overheating, coolant loss, and/or misfire. In some cases, DTCs P0300 through P0304 may also be stored (DTCs are not required for repair).
- A26-019 Service bulletin2026-09-25 · Engine
- Service Bulletin - Under certain conditions, the cylinder head gasket effectiveness may be reduced which may cause vehicles to experience overheating, coolant loss, and/or misfire. In some cases, DTCs P0300 through P0304 may also be stored (DTCs are not required for repair).
- A26-017 Service bulletin2026-09-25 · Engine
- Service Bulletin - Under certain conditions, the cylinder head gasket effectiveness may be reduced which may cause vehicles to experience overheating, coolant loss, and/or misfire. In some cases, DTCs P0300 through P0304 may also be stored (DTCs are not required for repair).
- A26-016 Service bulletin2026-09-25 · Engine
- Service Bulletin - Under certain conditions, the cylinder head gasket effectiveness may be reduced which may cause vehicles to experience overheating, coolant loss, and/or misfire. In some cases, DTCs P0300 through P0304 may also be stored (DTCs are not required for repair).
- A26-013 Service bulletin2026-09-25 · Engine
- Service Bulletin - Under certain conditions, the cylinder head gasket effectiveness may be reduced which may cause vehicles to experience overheating, coolant loss, and/or misfire. In some cases, DTCs P0300 through P0304 may also be stored (DTCs are not required for repair).
- A26-012 Service bulletin2026-09-25 · Engine
- Service Bulletin - Under certain conditions, the cylinder head gasket effectiveness may be reduced which may cause vehicles to experience overheating, coolant loss, and/or misfire. In some cases, DTCs P0300 through P0304 may also be stored (DTCs are not required for repair).
What P0304 means
Source: SAE J2012 / OBD-IICylinder 4 is misfiring.
A stored code names the test that failed, never the part that caused it. It is the starting point of a diagnosis, not its conclusion — the same code has several possible causes and the cheap one is not always right.
Common questions about P0304
Source: NHTSA files and the OBD-II standardCan I keep driving with P0304 stored?
Nobody can answer that from the code alone, and a site that does is guessing. A steady light means a fault was logged and the car should be checked soon; a flashing light means a severe misfire — slow down and get it seen as soon as possible, because severe misfire can quickly damage the catalytic converter. The safe read of this page is the mileage and the components, not permission.
Does a code mean the car is recalled?
No. Recalls are filed by campaign and matched by VIN, and none of them are triggered by a scan tool. If you want to know whether an open recall applies to one specific vehicle, check the VIN at nhtsa.gov/recalls — that is the only source that settles it.
Why do the counts here differ from other sites?
Because these are not estimates. Every number on this page is a count of documents in NHTSA's own files: manufacturer communications that name the code in their filed summary, and owner complaints that name it in the narrative. We do not model, weight or extrapolate them.
Will clearing the code fix it?
Clearing turns the light off and erases the freeze-frame data a technician would have used to work out what happened. If the condition is still there the code returns, usually within a few drive cycles, and the diagnosis now starts from less information than before.