P0304 on Honda vehicles Cylinder 4 is misfiring

A model year is listed because the code is named in its own record — a bulletin filed against it, or an owner’s complaint about it — not because every one of these vehicles sets it. Counts are documents in NHTSA’s files, not failure rates.

Owners’ own words, scrubbed of anything identifying. Unverified reports filed with NHTSA — what was said, not a finding that it was true.

Bulletins and campaigns Honda filed with NHTSA whose summary names P0304. Quote the document number at the service desk — it is a diagnosis the maker has already written down.

• A18-114 Service bulletin
  2018-10-22 · Engine And Engine Cooling
• Service bulletin - Under certain circumstances, the vehicle may experience driveability concerns, which may result in DTC's 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), or P0172 (Fuel System Too Rich) to set.
• A18-124 Service bulletin
  2018-10-22 · Engine And Engine Cooling
• Service bulletin - Under certain circumstances, the vehicle may experience driveability concerns, which may result in DTC's 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), or P0172 (Fuel System Too Rich) to set.
• A18-114 Service bulletin
  2018-12-07 · Electrical System — Software
• "Service bulletin - Under certain circumstances, the vehicle may experience driveability concerns, which may result in DTC's 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), or P0172 (Fuel System Too Rich) to set."
• A19-027 Service bulletin
  2019-03-05 · Equipment — Appliance — Air Conditioner
• Service Bulletin - Under certain circumstances, the vehicle may experience driveability issues, which may result in DTCs 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), or P0172 (fuel system too rich) to set.
• A19-012 Service bulletin
  2019-04-05 · Equipment — Appliance — Air Conditioner
• Service Bulletin - This bulletin is replaced by S/B 19-033, Warranty Extension: 2016-18 Civic 1.5L: Software Update with A/C Control Unit Replacement; DTC P0300, P0301, P0302, P0303, P0304, or P0172; Whirling Noise from Engine. If you did Service Bulletin 19-012 on or before April 5th, 2019, use the Warranty Claim Information provided below.
• A19-012 Service bulletin
  2023-01-11 · Visibility
• Service Bulletin - This bulletin is replaced by S/B 19-033, Warranty Extension: 2016-18 Civic 1.5L: Software Update with A/C Control Unit Replacement; DTC P0300, P0301, P0302, P0303, P0304, or P0172; Whirling Noise from Engine.
• A26-003 Service bulletin
  2026-08-26 · 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.
• A26-004 Service bulletin
  2026-08-26 · 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.
• AEBM08262026901 Other
  2026-08-26 · 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.
• A26-008 Service bulletin
  2026-08-26 · 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.
• A26-009 Service bulletin
  2026-08-26 · 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 Service bulletin
  2026-09-25 · 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).

A stored code names the test that failed, never the part that caused it. The record above is what Honda and its owners have filed about it; the code’s page across every make has the whole file.