P0304 on the 2021 Honda Accord
The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.
Nobody has written a description of this code yet.
| A26-006 | 2026-10-01. Service bulletin. 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). |
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| A26-003 | 2026-10-01. Service bulletin. 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). |
| AEBM08262026901 | 2026-08-27. Other. Dealer Message - Under certain conditions, the cylinder head gasket effectiveness may be reduced which may cause vehicles to experience overheating, coolant loss, misfire, and/or DTCs P0300 through P0304 stored. |
| A26-006 | 2026-08-27. Service bulletin. Service Bulletin - Under certain conditions, the cylinder head gasket effectiveness may be reduced which may cause vehicles to experience overheating, coolant loss, misfire and/or DTCs P0300 thru P0304 stored. |
| A26-003 | 2026-08-24. Service bulletin. Service Bulletin - Under certain conditions, the cylinder head gasket effectiveness may be reduced which may cause vehicles to experience overheating, coolant loss, misfire and/or DTCs P0300 thru P0304 stored. |
| A23-026 | 2023-03-23. Service bulletin. Service Bulletin - Under certain circumstances, the vehicle may experience driveability concerns. This may result in the following DTC’s to set: • P0300 (Random Misfire Detected), • P0301 (No. 1 Cylinder Misfire Detected), • P0302 (No. 2 Cylinder Misfire Detected), • P0303 (No. 3 Cylinder Misfire Detected), • P0304 (No. 4 Cylinder Misfire Detected), • P0172 (Fuel System Too Rich) |
6 on file from NHTSA, as of 2026-10-19. See them in the bulletin list. A bulletin lists model years: read the document for which vehicles it concerns.