Service bulletins for the 2021 Honda Accord
A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.
175 on file from NHTSA, as of 2026-10-19.
About P0304 on the 2021 Honda Accord: what the code means, and the bulletins and recalls about the same components.
By type
By component
By trouble code
Only bulletins with trouble code: P0304 are shown. Show all
| A26-006 | 2026-10-01. Service bulletin. 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). |
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| A26-003 | 2026-10-01. Service bulletin. 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). |
| AEBM08262026901 | 2026-08-27. Other. ENGINE. 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. ENGINE. 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. ENGINE. 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. ENGINE AND ENGINE COOLING. 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) |
The summaries are NHTSA's. Each bulletin's page links NHTSA's copy of the manufacturer's document.