P0303 Code: Is Your Cylinder 3 Misfire a Cheap Fix?

A P0303 code means your engine computer caught cylinder 3 misfiring: the fuel and air in that cylinder aren't burning when they should. It's an OBD-II diagnostic trouble code (DTC) from your car's self-check system, EOBD on European cars, and it's what turns on the check engine light, steady or flashing.

In 25 federal complaints, new plugs or coils didn't cure P0303. In at least 12 of those, a dealer or mechanic went on to blame coolant in the cylinder, a head gasket or the engine itself.

That's why this page puts the free checks and the warranty check before the parts. It's built from the carmakers' own bulletins, six owner's manuals and 362 federal complaints about this code.

What does P0303 mean?

It stands for cylinder 3 misfire detected: the computer counted enough misfires in cylinder 3 to raise emissions or harm the catalytic converter, which cleans the exhaust. Scan tools print it as P0303 or P030300, and people also type PO303, with a letter O, or P303.

If P0300, the random misfire code, sits beside it, more than one cylinder may be missing, and 67 of the 362 federal complaints naming P0303 list both. How the computer chooses between the two is on the P0300 page, our guide to every misfire code.

Owners describe these signs in the 362 complaints:

• Stalling.69 complaints say the engine stalled or shut off, some of them on the highway.
• Lost power or hesitation.56 complaints; jerking when accelerating covers how that feels.
• Shaking or vibration.48 complaints, because cylinder 3 isn't doing its share of the work.
• A flashing check engine light.36 complaints, the sign of a misfire heavy enough to harm the converter.
• A rough idle.20 complaints, the shake you feel while you're stopped.
• Overheating or white smoke.40 and 22 complaints, the signs that coolant may be getting into the cylinder.

Can you drive with a P0303 code?

Yes, gently, if the light is steady, and get it to a shop soon; if it flashes, slow down and stop as soon as it's safe. If the coolant keeps falling, stop driving and have it checked, because an engine losing coolant can overheat.

Three owner's manuals agree on the flashing light: the 2012 F-150, 2020 Silverado and 2018 Accord all say to ease off and get the car to a shop soon. Honda's goes furthest: park away from anything flammable, stop the engine for at least 10 minutes, and if the light blinks again after a restart, drive to a dealer at 31 mph or less.

A misfire can also stall the engine, which 69 complaints describe. A 2018 CR-V owner wrote that on the highway it shut down and lost all power (complaint 11184408).

If yours has already stalled, keep it off busy roads until it's fixed. The flashing check engine light guide covers what the blink means on any code, and what each manual says is set out on the P0300 page.

What causes a cylinder 3 misfire?

Either something that feeds cylinder 3 has failed, or something inside the cylinder has. The first three below are the parts that feed it; the last five are faults a new plug, coil or injector won't fix.

1. Spark plug

The plug makes the spark that lights the fuel. Worn, oily or wet with coolant, it can't, and how it looks when it comes out tells you what's behind it.

Chrysler replaces all six plugs, for an internal crack, on 3.6L V6s built in September 2020, from the 2020 Pacifica to the 2021 Ram 1500.

2. Ignition coil

The coil turns battery power into the high voltage the plug needs. On engines with one coil sitting on each plug, that's what makes the free swap test possible.

Kia replaces all four coils on some 2017 and 2018 Forte 2.0L cars with a misfire code.

3. Fuel injector

The injector sprays fuel into the cylinder, so a clogged or failed one leaves nothing to burn. Owners name injectors in 51 of the 362 complaints.

Hyundai and Kia replace injectors for misfire codes, P0303 among them, on some 2.5L engines from 2021 on.

4. Coolant in the cylinder

Coolant, the fluid that carries heat away from the engine, can leak into a cylinder through a failing head gasket or corrosion in the block. The plug gets wet, you'll see the level in the tank keep dropping, and new plugs or coils only buy you time.

Ford's 1.5L and 2.0L EcoBoost engines are the documented case, and Honda covers head gaskets on newer models; both are in who pays.

5. Worn piston rings

Piston rings seal the cylinder and keep oil out of it. On the 2013 to 2015 Honda Pilot and 2013 to 2017 Odyssey, Honda says the rings can stick, so oil reaches the plug and fouls it.

How Honda's technicians check for it on those cars, starting at the No. 3 plug, is under telling the coil from the cylinder.

6. Intake or charge air damage

On the 2014 to 2017 Ford Fusion and 2017 Escape 1.5L, an intake manifold bolt can back out and damage the charge air cooler. That's the radiator that cools air from the turbo, and low coolant and white smoke come with it.

On the 2021 F-150 PowerBoost, a restricted air pipe on the right turbo can set P0301 to P0303 along with P0299, and the engine cuts its power.

7. Worn valvetrain

The valvetrain is the set of parts that opens and closes each cylinder's valves: lifters, roller followers and lash adjusters. When one wears, the cylinder can't breathe properly, and sometimes you'll hear a tick.

GM and Toyota both name these parts for P0303 on some engines, listed in which cars.

8. Engine software

Sometimes the engine computer misjudges a cold start, and the fix is an update rather than a part.

Honda does it on the 2018 to 2022 Accord 2.0L, and Nissan on the 2022 Frontier.

A vacuum leak near cylinder 3 is another suspect, but no carmaker document we read names one for P0303, and only one complaint mentions it. Treat it as a check, not a known cause.

How much does it cost to fix P0303?

Each part costs under $100 at the counter on the three cars we priced, so labor and the cause decide the bill. The box below prices the parts on the Accord, the F-150 and the Escape, beside US averages for the same jobs at a shop.

If the fault is one a new plug, coil or injector won't fix, you pay far more, mostly in labor. Here are the hours two makers allow for two of those repairs, priced at $120 to $159 an hour, a common independent-shop rate:

• Honda, 8.9 hours.The rings in cylinders 1 to 3 on a 2013 to 2015 Pilot: $1,068 to $1,415 before parts.
• Ford, 4.3 to 5.1 hours.The intake manifold and charge air cooler on a 1.5L Fusion or Escape: $516 to $811 before parts.

A misfire left alone can also ruin the catalytic converter, which CarMD puts at $1,511 on average. If the head gasket has gone and nobody covers it, head gasket replacement cost covers what that job runs.

Where is cylinder 3?

Cylinder 3's location depends on how the maker numbered that engine, so the answer is in its service information, not in a rule of thumb. Your owner's manual rarely helps.

Of the six manuals we read, only the 2012 F-150's prints a firing order. That's the order the cylinders fire in, not where they sit.

Honda's bulletins do place it on the 3.5L V6 in the 2013 to 2015 Pilot and 2013 to 2017 Odyssey. For P0301, P0302 or P0303 they send the technician to the rear cylinder head, so cylinder 3 sits there with 1 and 2.

Chrysler's 2014 bulletin for its 2011 to 2013 3.6L V6 tests cylinders 2, 4 and 6 before it replaces the left head. It never names cylinder 3, so ask the shop which head it's on.

On any other engine, ask the shop to point at coil 3 before anything is unplugged. How makers number cylinders, and why counting from the front of the car is a guess, is on the P0300 page.

How do you tell the coil from the cylinder?

Swap coil 3 with a neighbor's, clear the code and drive. If the misfire moves to the other cylinder, the coil is bad; if P0303 comes back, look at the plug next.

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The swap costs nothing, and dealers use it too. A 2014 Kia Soul owner quotes the dealer's report: Swapped Cylinder 3 coil pack and cylinder 1 coil pack (complaint 11525628).

The dealer then replaced the cylinder 1 coil, the one the misfire had followed, along with the plugs. If the misfire stays in cylinder 3 instead, the makers test the cylinder:

• GM: compression first.When the usual checks come up empty, its misfire guide compares how well each cylinder holds pressure, and a weak one leads to a leak test and the valvetrain.
• Ford: a pressure test for coolant.On the 2.0L EcoBoost, Ford pressurizes the cooling system to 20 psi, pounds per square inch, for 5 hours. A drop of 4 psi sends the technician looking for coolant in the cylinders.
• Ford, newer Escapes: a camera first.On 2023 to 2025 Escapes and Lincoln Corsairs with the 1.5L or 2.0L, a damaged plug sends the technician to a borescope, a camera on a cable, to look at the piston and cylinder walls before any head comes off.
• Honda: the plug, then the bore.On the Pilot and Odyssey 3.5L, a fouled No. 3 plug leads to the rear head and the rings.

Can you fix P0303 without replacing the coil or plug?

Sometimes. These cost you little or nothing, and each one either fixes it or tells you which part to buy:

• The coil swap.Moving coil 3 costs nothing and tells you whether a coil is worth buying at all.
• Reading the plug.The old plug's condition tells a shop whether the fault is the plug or something past it.
• A software update.Honda fixes a cold-start misfire on the 2018 to 2022 Accord 2.0L with one. Kia and Hyundai have updates for several Forte, Soul, Elantra and Tucson years.
• A carbon cleaning.On some 2016 to 2020 Honda Fits, carbon on the intake valves can cause the misfire. Honda's fix is a shop cleaning of the intake ports, with a software update on some.

Fuel additives and injector cleaners are the other thing people try. None of the carmaker documents we read recommends one for a misfire, so we can't point you to one that fixes it.

Four mistakes show up in the complaints and the bulletins:

• New plugs and coils when coolant is the cause.In 25 complaints new plugs or coils didn't cure the code. In at least 12 of those, a dealer or mechanic went on to blame coolant, a head gasket or the engine: 8 Fords, 3 Chrysler Pacificas and a Honda Accord.
• Buying parts before testing.A 2018 Hyundai Elantra owner replaced all four plugs and coils, then all four injectors and the wiring harness, and P0303 kept coming back (complaint 11699689).
• Missing the maker's bulletin.On 2020 to 2024 Forte and 2020 to 2022 Soul 1.6L turbos, Kia traced misfires that survive new plugs, coils and injectors to the alternator pulley.
• Blaming the catalytic converter.The converter is what a misfire damages, not what causes it, so a new one leaves the misfire in place.

Who pays for a P0303 repair?

On a few engines the carmaker pays, even past the normal warranty, if the cause matches its program. A dealer checks each one by VIN, your car's 17-character vehicle identification number:

• Ford Escape and Fusion 1.5L, 2017 to 2019.Program 21N12 replaces the short block, the engine's lower half, when coolant gets into the cylinders: 7 years or 84,000 miles from the warranty start date. The catch-up window for cars already past that closed on November 30, 2022.
• Ford Edge and other 2.0L EcoBoost models.Ford documents the same coolant problem on the 2015 to 2018 2.0L, but the bulletins we read give it no extended coverage; repairs go through Ford's normal approval process.
• Honda Accord, Civic and CR-V.Honda covers the head gasket for 10 years from purchase or 150,000 miles when a dealer finds coolant in a cylinder. It applies with misfire codes P0300 to P0304, and the P0304 page lists the model years.
• Honda Pilot 2013 to 2015 and Odyssey 2013 to 2017.Worn piston rings are covered for 10 years from purchase or 150,000 miles.
• Kia Soul 2012 to 2016, 1.6L.Recall 19V-120 updated their engine software to keep the catalytic converter from overheating. On Souls that had it, Kia's follow-up bulletin replaces the converter when code P0420 is stored, and the engine too if a misfire code is active and compression fails. There's no charge to you.
• Honda CR-V 2017 and 2018, and Civic 2016 to 2018, 1.5L turbo.Two 2019 extensions named P0303 and ran 6 years from the original sale, so nearly all of those cars are past them; a dealer can confirm.

Before you go, our free VIN checker shows open recalls and owner complaints for your model year. Ford and Honda mail owners about these programs, and a dealer can confirm any car by VIN; their own words are quoted below.

Which cars get P0303 most?

The Ford Escape leads the federal complaint record, with almost twice as many as the next model. Here are the five models named most:

Complaints show who filed, not how likely your car is to get the code. What your carmaker's own documents say about P0303:

GM's diagnostic bulletin for its pushrod V6 and V8 engines, including the V8s in Chevy and GMC pickups, lists P0303 among the codes a worn cam lobe, lifter or valve can set. If yours ticks, new plugs and coils won't touch that.

How do you fix a P0303 code?

Start with what's free and buy nothing until a test points at it. To fix a P0303 code, go through the 7 steps below in order:

1. Read every code and save the freeze frame. The freeze frame is the snapshot the computer takes when a code sets. If P0316 shows up too, note it: Ford's coolant bulletins list it with the misfire codes beside P0303.
2. Check the coolant level with the engine cold. If it keeps dropping and you can't find a leak, stop driving and have the cooling system pressure-tested.
3. Run the VIN. A dealer checks it for Ford's 21N12 and Honda's ring and head gasket coverage. Our free VIN checker shows open recalls and complaints for your model year.
4. Swap coil 3 with a neighbor's. Clear the code and drive; if the misfire moves with the coil, replace that coil.
5. Pull and read the No. 3 plug. Wet with coolant, black with oil or cracked, it's pointing past itself. On many 2010 to 2019 GM V6s, the Traverse, Acadia, Enclave and Camaro among them, fluid coming out of the plug tube itself means a porous cylinder head, and GM replaces the head.
6. Have the injector tested. A shop runs a balance test, which compares the fuel pressure drop across the injectors; GM's misfire guide lists it and warns it's only a first check.
7. Then test the cylinder. A compression test and a leak test show whether the rings, valves or head gasket are to blame, which is when a warranty extension matters most.

Steps 2 to 5 you can do yourself; from the injector on, it's shop work.

A quote for a new engine with no leak test or pressure test behind it skips steps Ford, GM and Honda all write down. Reading a repair estimate shows what else to look for.

What to ask the shop

Five questions that show whether a P0303 quote rests on tests or on guesses:

• Did you swap coil 3?If the misfire moved with it, the coil is bad; ask whether the plugs and the coil's ground were checked too. On GM's 3.6L V6 in the 2009 Traverse and Acadia, a worn or cracked plug or a loose ground can damage a coil, so a new coil alone may fail again.
• What did the No. 3 plug look like?Oily, wet or cracked means the cause is past the plug.
• Is the coolant dropping?If it is, ask for a pressure test before any parts go in.
• Did you test compression and leakage?An engine quote with no test behind it is a guess.
• Did you check my VIN for a program?It's the fastest way to confirm Ford's 21N12 or a Honda extension, especially on a car bought used.

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Common questions

Asked most often

What is the most common cause of a P0303 code?

Owners name the spark plug and coil most often: plugs come up in 100 of the 362 federal complaints and coils in 69. On Ford's 1.5L and 2.0L EcoBoost engines, coolant getting into the cylinder is the documented cause.

How serious is a cylinder 3 misfire?

It depends on the light and the coolant. A steady light and a full coolant tank mean get it fixed soon; a flashing light puts the catalytic converter at risk and falling coolant the engine, so stop driving for either.

How long can you drive with a P0303 code?

No carmaker gives a mileage. The manuals say to get it to a shop soon, and Honda's says that if the light blinks again after a restart, drive to a dealer at 31 mph or less.

Where is cylinder 3 located?

It depends on the engine, so ask a shop to point at it before you unplug anything. On Honda's 3.5L V6 in the Pilot and Odyssey, Honda's bulletins put cylinder 3 on the rear cylinder head, with 1 and 2.

Why is there a P0303 after changing the spark plugs?

Then the plug probably wasn't the cause. In 25 federal complaints new plugs or coils didn't cure the code, and in at least 12 of those a dealer or mechanic went on to blame coolant, a head gasket or the engine, so check the coolant and test the cylinder next.

Is P0303 covered by warranty?

On some engines, past the normal warranty. Ford covers coolant intrusion on the 2017 to 2019 Escape and Fusion 1.5L for 7 years or 84,000 miles, and Honda covers head gaskets, and Pilot and Odyssey rings, for 10 years or 150,000 miles, each checked by VIN.

Prices are ranges compiled in September 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.