Short answer
Most often ignition coils or spark plugs
P0300 is a misfire the computer couldn't pin to a single cylinder, which points at something shared rather than something local. The five commonest repairs behind it run $256 to $480 as US averages. If the lamp is flashing rather than steady, that's a defined signal with its own rule attached, and it changes what you do in the next five minutes.
OilAndMiles.com - A P0300 code is the computer reporting that combustion failed often enough to matter, across more than one cylinder or without a cylinder it could name. Almost every page about it goes straight to a list of causes.
The list is fine. What every one of those pages skips is that the regulation behind the code defines two different misfires and gives each one its own signal, and that the difference between them is the difference between an appointment and a roadside stop. The signal is the lamp itself, and steady or flashing is the whole of it.
The cylinder-specific codes, P0301 through P0308, name a cylinder by number, and that number belongs to the engine's own scheme rather than to anything you can count from the front of the car. This page covers the whole family, including the coil circuit codes, because they're one discussion. A reader holding P0303 and a reader holding P0352 are looking at the same fault from two directions.
What is a P0300 code actually measuring?
The computer isn't listening for a bang that didn't happen. It watches how evenly the crankshaft accelerates, and a cylinder that fails to fire leaves a gap in that rhythm. Count the gaps against the number of combustion events that should have occurred and you've what the regulation calls the percentage of misfire.
California's OBD II regulation, 13 CCR 1968.2, which the EPA accepts in place of its own, defines that term precisely: the percentage of misfires out of the total number of intended combustion events for a specified interval. Two intervals are used, and they aren't interchangeable. One runs over 200 engine revolutions, the other over 1,000.
There's no published percentage that trips the code. The thresholds are set against each engine's own emission standard rather than fixed in the rule. If you've read that a misfire code arrives at 2% or 4% of firing events, that figure is in wide circulation and it's not in the regulation.
Why does the lamp flash on some misfires and not others?
Because the regulation splits misfire into two tiers, and only the tier that threatens the catalyst gets the flash:
| What the computer saw | What the lamp does | How it is judged |
|---|---|---|
| Enough misfire to damage the catalyst | Flashes, once a second | Judged over 200 engine revolutions, fast enough to warn you as it happens. The rule sets the rate: blink once per second |
| Enough misfire to breach the emission standard | Steady, from the next drive | Assessed over 1,000 revolutions. Over the limit rather than on fire, so it waits for the next driving cycle that monitors |
| The percentage that trips either one | Not published | The rule defines percentage of misfire but sets the thresholds against each engine's own emission standard, so there's no single figure to quote |
We went to the regulation for those two windows rather than to a repair site, because the numbers people quote for a misfire percentage aren't in it. The rule sets each threshold against the engine's own emission standard, so we can't give you a percentage and neither can anybody else.
One bulb carries both messages, in the same place on the dash. The rate is the whole difference, and no other telltale on the car works that way. The definitions come from the California OBD II regulation, 13 CCR 1968.2, subsection (e)(3), which the EPA accepts in place of its own.
Manufacturers say the same thing in plainer words. Honda's own owner's manual for the 2020 Civic describes the malfunction indicator lamp as blinking when a misfire in the engine's cylinders is detected, and its instruction for a lamp blinking while driving is unusually specific: stop in a safe place where there are no flammable objects, stop the engine for ten minutes or more and let it cool, then take the vehicle to a dealer.
That instruction is worth reading twice. A manufacturer is telling you to park away from anything that burns, which is a statement about how hot the exhaust gets when unburnt fuel is arriving in it. Our article on the flashing check engine light works the same chain from the temperature end.
How is P0300 different from P0301 through P0308?
P0300 is the random or multiple misfire: the computer saw misfires it couldn't assign to one cylinder, either because more than one was involved or because the pattern moved around. The lamp itself waited two drives before telling you, which is what the light means. That points away from a part attached to one cylinder and towards something shared: fuel pressure, a vacuum leak, a lean mixture code, timing.
P0301 through P0308 each name a cylinder, so a P0302 code is cylinder two and a P0303 code is cylinder three. Those point the other way: a coil, a plug, an injector, a compression problem on that one cylinder, and on some Ford EcoBoost engines coolant getting into it, which the P0301 page covers.
Seeing P0300 alongside P0303 is the most useful combination of all, because the computer has found a general misfire and pinned one cylinder inside it. Start with the named one.
| What you're looking at | What it tells you | What it doesn't |
|---|---|---|
| The last digit is the cylinder | P0303 means cylinder 3. P0301 through P0308 each name one | P0300 names none of them, which is why it is called a random misfire |
| Numbering is set by the engine | Some makers number 1, 2, 3 down one bank and 4, 5, 6 down the other. Others alternate odd and even across the two banks | Cylinder 3 isn't the third one you can see from where you're standing |
| P0300 with no companion code | More than one cylinder, or a cause that isn't cylinder specific: fuel pressure, a vacuum leak, a mixture problem | Look for something shared rather than something local |
| P0300 alongside P0303 | The computer has seen a general misfire and pinned one cylinder inside it. A stronger lead than either code alone | Start with the named one |
Owner's manuals don't carry cylinder numbering or firing order. That's service manual material, and it's the first thing to look up on this code. The wrong coil pulled is time spent and nothing learned.
Which cylinder is cylinder three?
The last digit of the code is the cylinder number, and that number belongs to the engine's numbering scheme. The scheme isn't universal.
Some manufacturers number one bank of a V engine 1, 2, 3 and the other 4, 5, 6. Others alternate odd and even across the two banks. On an inline engine it is usually simple; on a V engine it frequently isn't.
So P0303 isn't reliably the third cylinder counting from the front of the car, and pulling the third coil you can see is a way to spend twenty minutes learning nothing. Look up the numbering for that specific engine first. It won't be in the owner's manual, which carries neither firing order nor cylinder numbering, because that's service manual material.
Worth knowing
The coil circuit codes, P0351 through P0354, belong in this conversation rather than in a separate one. A reader holding P0351 has a misfire and a computer that has identified the circuit behind it. The diagnosis converges on the same components from a shorter distance.
What does the suffix after the code mean?
More people search this code with a manufacturer attached than without one: P0300 Chevy, P0300 Silverado 1500, P0300 Ford, P0300 Nissan, P0300 Toyota, P0300 Dodge. The answer to all of them is the same, and it's the useful part.
P0 codes are standardized by regulation, not by convention. The EPA's on-board diagnostic rules at 40 CFR 86.1806 name SAE J2012, the standard that defines what the characters in a diagnostic trouble code, or DTC, mean, and require the results to be readable by any scan tool in a standardized format. A zero in the second position marks the generic set.
So P0300 means a random or multiple cylinder misfire on a Silverado, a Camry and a Ram alike. Our piece on reading the four characters covers how the rest of the structure works.
What differs by make isn't the code. It's which components fail often enough on that engine to be worth checking first, and that's a question for a forum or a service bulletin rather than for the code definition.
The suffix is a different matter. GM scan data commonly shows P0300-00 or P0300:00, and people reasonably assume it is a different code. It's not.
Those two extra digits are a failure type byte, the standardized subtype set that SAE J2012 places in its J2012-DA annex and that applies only where three-byte codes are in use. The base code in front of it still means exactly what it means everywhere else.
Which swap answers it without buying a part?
If the code names a cylinder, there's a test that costs nothing. Move the coil from the cylinder the code names onto a different cylinder, clear the code, and drive.
If the code follows the coil, the coil is the fault. If it stays with the original cylinder, the coil is fine and the problem is the plug, the injector or the cylinder itself.
The swap isn't a manufacturer's procedure and we aren't presenting it as one. It follows from the fact that the code names a cylinder, and it's the reasoning rather than a citation.
Two cautions. Note which coil went where before you start, and don't run an engine that is misfiring badly for longer than the test needs, for the reason in the section above.
Which cars report a misfire code most?
No make stands out, and that's the finding rather than a disappointment. Across 645,169 complaints the highest share is GMC at 0.14% and the next is 0.11%, which is a spread narrow enough to be noise. A misfire is a combustion fault, and every engine burns fuel the same way.
What the table is good for is the opposite question: it shows which vehicles turn up in the record at all, which is mostly a function of how many were sold and how willing their owners are to file.
From the national complaint record
0.14%
of GMC complaints name P0300. It's the highest here, but only just: the next is 0.11%, and the spread across the whole list is narrow. Read this as the vehicles that show up, not as a ranking with a leader.
| GMC | 0.14% | 28 of 20,597 | |
|---|---|---|---|
| Chevrolet | 0.11% | 63 of 58,248 | |
| Honda | 0.09% | 42 of 46,500 | |
| Kia | 0.08% | 27 of 32,602 | |
| Ford | 0.07% | 90 of 130,824 | |
| Hyundai | 0.05% | 21 of 40,008 | |
| Ram | 0.05% | 10 of 19,696 | |
| Jeep | 0.04% | 19 of 42,325 |
What does a P0300 code cost to fix?
The repairs behind a misfire are among the cheapest on the national list. From the CarMD Vehicle Health Index for 2026, built from 39,116,755 repairs recommended in 2025, replacing ignition coils averaged $256, spark plugs $299, coils and plugs together $480, and fuel injectors $572.
Left alone, it becomes the most expensive item on the same list. Replacing a catalytic converter averaged $1,511 and took first place for the second year running, and the converter replacement cost range runs from $650 to $2,500. The raw fuel a misfire sends into the exhaust burns inside the converter, which is precisely what the flashing lamp is there to prevent.
What a P0300 code costs to fix, cheapest first
Separate repairs, so there's no total: you pay one of them, not the set.
| Ignition coilsThe cheapest of the five most common | $256Parts and labor, US average |
|---|---|
| Spark plugsOften done with the coils | $299Parts and labor, US average |
| Ignition coils and spark plugsThird most common repair of the year | $480Parts and labor, US average |
| Fuel injectorsWhere a cylinder-specific misfire goes next | $572Parts and labor, US average |
| Catalytic converterWhat an ignored misfire turns into | $1,511Parts and labor, US average |
CarMD Vehicle Health Index 2026, US averages across 39,116,755 repairs recommended in 2025, parts and labor together, read August 25, 2026.
A misfire left alone is the most common way a converter dies, and the four cheaper repairs above are all cheaper than the converter. We set out what kills one, and what each preventing repair costs, in what a catalytic converter is.
What should you do about a P0300 code?
Five steps for finding which cylinder is misfiring, and why, before anyone sells you parts. The lamp decides the first one, and everything after that is cheap before it is expensive. 5 steps below:
- Look at the lamp before you look at the code. Flashing means stop where nothing can catch fire, shut the engine down, let it cool. Steady means drive to an appointment rather than to a roadside.
- Read the whole set of codes, not one. P0300 with a cylinder code beside it is a different lead from P0300 on its own. Reading is free at most US parts chains.
- Look up the cylinder numbering for that engine. Before touching anything, and before buying a part. It's in the engine's service information rather than the owner's manual, and a parts counter or a repair database can tell you in a minute.
- Swap the coil if the code named a cylinder. The code either follows it or it doesn't, and either answer costs nothing.
- If the code is P0300 alone, stop looking at one cylinder. Fuel pressure, vacuum leaks and mixture faults affect all of them, and that's what a random misfire is telling you.
Conclusion
Something shared, not something local
A random misfire points at something shared, not something local. The computer couldn't attribute it to one cylinder, and that's the information the code carries: fuel, spark or air common to all of them rather than a single coil or plug. A code naming a cylinder would be a different article.
The lamp decides urgency before the code decides anything, and a flashing one means stop where nothing can catch fire rather than drive to an appointment. Oil & Miles reads the lamp, then the code, then the price, across symptoms.
Common questions
Asked most often
Can a bad MAF sensor cause a P0300 code?
Yes, and it fits the code's own logic. A mass airflow sensor that reads wrong mis-meters the air for every cylinder at once, which is a shared fault rather than a local one, and shared is what P0300 means. A single failed coil usually sets a cylinder-specific code instead.
Can you drive with a P0300 code?
With a steady lamp, to an appointment, yes. With a flashing lamp, no: the regulation reserves that signal for a misfire severe enough to damage the catalytic converter, and Honda's own manual tells drivers to stop and let the engine cool for ten minutes.
What is the most common cause of P0300?
Because it is the random misfire, the causes that fit are the shared ones: fuel delivery, a vacuum leak, a mixture problem such as a mass airflow sensor reading wrong, or worn plugs across the whole set. A single failed coil usually produces a cylinder-specific code instead.
Does P0301 mean cylinder one?
It means cylinder one in that engine's numbering, which isn't necessarily the first cylinder you can see. Some engines number one bank then the other, some alternate across banks. Look the numbering up before pulling anything. What causes a cylinder 1 misfire, and the Ford engines where it means coolant, is on the P0301 page.
How much does it cost to fix a misfire?
Nationally in 2025, ignition coils averaged $256, spark plugs $299, and the two together $480. Fuel injectors run $572. All of them are a fraction of the $1,511 converter the misfire is working towards.
What percentage of misfires sets the code?
There's no published figure. The regulation defines percentage of misfire but sets the thresholds against each engine's own emission standard, so the 2 to 4% quoted in many places has no regulatory basis.
Is P0351 the same problem as P0301?
Close enough to be one conversation. P0351 reports the coil circuit for a cylinder, so a reader holding it has a misfire and a shorter path to the part. The same swap test applies.
Is the second character in P0300 a zero or a letter?
A zero. Only the first character of the code is a letter, and the four after it are digits. On a scan tool the zero and a capital O look almost identical, so typing the letter into a parts catalog is an easy slip that returns nothing rather than correcting you.
What people ask next
- P0174 Code: The Bank 2 Code That Isn't About Bank 2 14 min
- P0172 Code: The Searches Say Chevy, the Record Says CR-V 14 min
- P0700 Code: The One That Points at Another Code 15 min
- P0301 Code: A Plug, a Coil, or Coolant on a Ford 18 min
- P0441 Code: Why the Toyota Answer Is Usually Wrong 12 min
- P0442 Code: Why a New Gas Cap Often Changes Nothing 13 min
Sources
- 13 CCR 1968.2, subsection (e)(3), read at source, for the two misfire tiers, the 200 and 1,000 revolution windows, and the once-per-second blink required at (e)(3.4.1)(A)(ii). California Air Resources Board, read August 2026
- Honda owner's manual, 2020 Civic, malfunction indicator lamp entry, read at source, for what the blink means and what Honda tells an owner to do. Honda is one manufacturer; others word it differently. Honda owner's manual, read August 2026
- CarMD Vehicle Health Index 2026, read as the published PDF, for every price on this page. CarMD sells diagnostic tools, an interest worth naming. CarMD.com Corp, read August 2026
- 40 CFR 86.1806 and SAE J2012, for the code format and the failure type byte. We give no meaning for the value 00: those definitions live in the J2012-DA annex, which we haven't read. SAE International and the eCFR, read August 26, 2026
- The coil swap test is reasoning, not a citation. It follows from the code naming a cylinder: move the coil, and the code either follows it or it doesn't. No source is offered because none is needed and none should be implied. Oil & Miles
How this was compiled
The complaint counts come from NHTSA's published bulk download rather than its search page, so the whole record is counted rather than a sample. The file is FLAT_CMPL, and the copy read here is dated 25 August 2026.
NHTSA files one row per component a complaint names, so the count is by complaint number rather than by row: across the 2010 to 2025 model years that is 645,169 complaints, and those are what was scanned for this article.
The article covers P0300 through P0308 and the coil circuit codes on one page rather than nine, because those codes differ by one digit and share every word of their explanation. It leads with the two tiers rather than with a list of causes, because the tier decides what a reader does in the next five minutes and the cause list does not.
What we didn't do
- We give no misfire percentage threshold. The regulation defines the term and then sets the limits against each engine's emission standard, so no single number exists to quote, and the figures in circulation aren't from the rule.
- We publish no cylinder numbering table by manufacturer. The sources for that are forums and content sites, and a wrong diagram would send somebody to the wrong coil.
- We didn't scan a car, clear a code or perform the coil swap for this article.
- We give no failure rates by component. Nothing published counts misfire causes in a way we would repeat.
Prices are ranges compiled in August 2026 for the US market and vary by region, engine and shop rate. Prices from $10 up are rounded to the nearest dollar, so $14.13 reads as $14 and $14.52 as $15. Below $10 they're exact. This article is general information, not advice about your specific vehicle, see the disclaimer.