The Lemon IndexCylinder 4 is not firing properly, so the engine runs rough and loses some power. Full P0304 page
19 owner complaints · the #5 code Honda Odyssey owners name · 7% of Honda Odyssey complaints that name a code (every car: 2.4%)
2003–2016 Honda Odyssey · most: 2013 (7), 2015 (4), 2014 (3)
Honda Odyssey owners named P0304 in 19 complaints to the U.S. government (NHTSA), most often on the 2013, 2015 and 2014 model years. The part they name most is the spark plugs (11 complaints). Complaints are owner reports, not proof of a defect.
Honda Odyssey 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 spark plugs, in 11 of the 19 complaints (58%). 9 of those mention it being replaced or repaired, and 5 say the problem came back afterwards. Next: pistons, rings or valves (10), engine software (a reflash) (4) and engine (replaced or rebuilt) (2).
- Spark plugs11 complaints9 mention a repair or replacement, 5 of them say the problem came back · what Honda Odyssey owners paid
- Pistons, rings or valves10 complaints6 mention a repair or replacement, 2 of them say the problem came back
- Software update (reflash)4 complaints3 mention a repair or replacement
- Engine replaced or rebuilt2 complaints2 mention a repair or replacement, 2 of them say the problem came back · what Honda Odyssey owners paid
- Ignition coils2 complaints1 mentions a repair or replacement, 1 of them says the problem came back · what owners paid
- Engine computer (ECM / PCM)2 complaints1 mentions a repair or replacement · what owners paid
5 complaints mention a recall and 14 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
42% of these complaints say the check engine light came on.
- Shakes, runs rough or misfires79%15 of 19 complaints
- Uses or leaks oil21%4 of 19 complaints
- Stalls or shuts off11%2 of 19 complaints
- Loses power or goes into limp mode11%2 of 19 complaints
- Warning lights and electrical faults11%2 of 19 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
Other codes named in the same Honda Odyssey complaints, and in how many.
Repair costs
Honda Odyssey spark plug replacement cost · Honda Odyssey engine replacement cost
Recalls on these Honda Odyssey years
- Engine · 2013 · issued 2013
During manufacturing of the engine piston, it is possible that the heat treatment process was not properly applied, resulting in the piston having an insufficient hardness level, making it more susceptible to premature w… NHTSA 13V382000
1 recall for the same systems (engine) on the Honda Odyssey 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 Odyssey reliability by year
- 2013 Honda Odyssey problems and recalls
Other codes Honda Odyssey owners report
U3000 P0740 P0730 P0301 P0303 P219A P0302 P0420 P3400 P3497
P0304 on other cars
Ford Escape (49) · Ford Edge (31) · Honda CR-V (23) · Honda Accord (20) · 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): 11753339, 11733841, 11724102, 11716004, 11698536, 11684172, 11683289, 11679980, 11679810, 11678822, 11676053, 11670811 and 7 more.
Quick answers
What does P0304 mean on a Honda Odyssey?
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 Odyssey years have the most P0304 complaints?
In complaints to NHTSA, owners of the 2013 (7), 2015 (4), 2014 (3) Honda Odyssey named P0304 most (19 complaints in all, 2003–2016). Raw counts, not a failure rate.
What fixes P0304 on a Honda Odyssey?
Owners most often name the spark plugs (11 of 19 complaints), then pistons, rings or valves and engine software (a reflash). 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 Odyssey 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 Odyssey, 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.