The Lemon IndexCylinder 4 is not firing properly, so the engine runs rough and loses some power. Full P0304 page
20 owner complaints · the #2 code Honda Accord owners name · 10% of Honda Accord complaints that name a code (every car: 2.4%)
2011–2022 Honda Accord · most: 2018 (9), 2019 (5), 2022 (2)
Honda Accord owners named P0304 in 20 complaints to the U.S. government (NHTSA), most often on the 2018, 2019 and 2022 model years. The part they name most is the head gasket (6 complaints). Complaints are owner reports, not proof of a defect.
Honda Accord model years that report P0304
Owner complaints naming P0304, by model year. Raw counts: years that sold more get more complaints, so this is each model year's record, not a failure rate.
What owners say caused it or fixed it
The most-named part is the head gasket, in 6 of the 20 complaints (30%). 2 of those mention it being replaced or repaired. Next: fuel injectors (5), spark plugs (4) and fuel pump (3).
- Head gasket or coolant in a cylinder6 complaints2 mention a repair or replacement · what Honda Accord owners paid
- Fuel injectors5 complaints2 mention a repair or replacement, 1 of them says the problem came back · what Honda Accord owners paid
- Spark plugs4 complaints3 mention a repair or replacement, 1 of them says the problem came back · what Honda Accord owners paid
- Fuel pump3 complaints3 mention a repair or replacement, 1 of them says the problem came back · what Honda Accord owners paid
5 complaints mention a recall and 4 mention a warranty.
Counted from the owners' own words: a part counts when a sentence names it with a cause or repair word. What owners wrote, not a diagnosis. A shop should confirm the cause before replacing parts.
Symptoms owners describe with P0304
40% of these complaints say the check engine light came on.
- Shakes, runs rough or misfires75%15 of 20 complaints
- Loses power or goes into limp mode45%9 of 20 complaints
- Flashing check engine light25%5 of 20 complaints
- Warning lights and electrical faults20%4 of 20 complaints
- Stalls or shuts off15%3 of 20 complaints
- Brakes or ABS act up10%2 of 20 complaints
Share of the complaints naming P0304 whose text also describes each problem. A complaint can describe more than one.
Codes owners report with it
P0300 8 P0301 7 P0302 3 P0303 3
Other codes named in the same Honda Accord complaints, and in how many.
Repair costs
Honda Accord head gasket replacement cost · Honda Accord fuel injector replacement cost · Honda Accord spark plug replacement cost · Honda Accord fuel pump replacement cost
Recalls on these Honda Accord years
- Fuel system, gasoline · 2016, 2018, 2019, 2020, 2021, 2022 · issued 2023
The fuel pump inside the fuel tank may fail. NHTSA 23V858000 - Fuel system, gasoline · 2019, 2020 · issued 2021
The low-pressure fuel pump inside the fuel tank may fail. NHTSA 21V215000 - Fuel system, gasoline · 2018, 2019 · issued 2020
The low-pressure fuel pump inside the fuel tank may fail. NHTSA 20V314000 - Fuel system, other · 2016 · issued 2019
Particulates in fuel may adhere to the internal components of the fuel pump, reducing its performance. NHTSA 19V060000
4 recalls for the same systems (engine and fuel) on the Honda Accord model years above. A recall for the same system isn't proof it's behind P0304. Recall work is free at any dealer: check a VIN at nhtsa.gov/recalls or with our VIN check.
Keep going
- P0304: meaning, causes and every car that reports it
- Honda Accord reliability by year
- 2018 Honda Accord problems and recalls
Other codes Honda Accord owners report
P0303 P0301 P0302 P0300 P0087 P0741
P0304 on other cars
Ford Escape (49) · Ford Edge (31) · Honda CR-V (23) · Honda Odyssey (19) · Ford Fusion (16) · Honda Pilot (14) · Kia Sorento (10)
The details
How we count
We read every owner complaint in the NHTSA file whose text names this trouble code, and count the ones filed about this model (matched by the make, model and model year on the complaint). Mileage is what the owner entered on the form.
Parts: a complaint counts for a part when one of the owner's own sentences names that part together with a cause word (failed, bad, diagnosed, caused by, leaking ...) or a repair word (replaced, repaired, new, reprogrammed ...). "Came back" means the same complaint also says the problem returned or the repair didn't fix it. These are counts of what owners wrote, not a diagnosis, and one complaint can name several parts.
Complaints are reports, not proof of a defect, and most owners never file one. Popular models get more complaints, so the counts are not a failure rate. The code meaning is the standard SAE J2012 definition in our own words, or the carmaker's meaning where we verified it for that make.
What P0304 means
Cylinder 4 is not firing properly, so the engine runs rough and loses some power. A flashing check engine light means the misfire is serious enough to damage the catalytic converter, so slow down and get it checked right away.
Get it fixed soon. A few more days of normal driving is usually OK, but waiting can turn a small repair into a bigger one or a breakdown.
- Spark plug or ignition coil on cylinder 4
- Fuel injector on cylinder 4
- Vacuum leak near that cylinder
- Low compression (valve or piston ring problem)
Check the complaints yourself
NHTSA complaint numbers (search them at nhtsa.gov): 11764231, 11742804, 11736450, 11730158, 11705033, 11704229, 11699319, 11695931, 11635157, 11614869, 11574002, 11559310 and 8 more.
Quick answers
What does P0304 mean on a Honda Accord?
Cylinder 4 Misfire Detected. Cylinder 4 is not firing properly, so the engine runs rough and loses some power. A flashing check engine light means the misfire is serious enough to damage the catalytic converter, so slow down and get it checked right away.
Which Honda Accord years have the most P0304 complaints?
In complaints to NHTSA, owners of the 2018 (9), 2019 (5), 2022 (2) Honda Accord named P0304 most (20 complaints in all, 2011–2022). Raw counts, not a failure rate.
What fixes P0304 on a Honda Accord?
Owners most often name the head gasket (6 of 20 complaints), then fuel injectors and spark plugs. That's what owners wrote, not a diagnosis: have a shop confirm the cause with a scan and tests before replacing parts.
Can I drive my Honda Accord with P0304?
Get it fixed soon. A few more days of normal driving is usually OK, but waiting can turn a small repair into a bigger one or a breakdown.
Sources: NHTSA owner complaints that name P0304 on the Honda Accord, counted by The Lemon Index; NHTSA recalls; repair bills owners named. Meanings: SAE J2012 in our own words. Owner reports, not a diagnosis or repair advice for your car.