P0303 Code in 2026: Cylinder 3 Misfire, the Coil Swap, and the Coolant Nobody Checks

P0303 tells you where the misfire is, not why.

Every time a cylinder fails to burn its charge properly, the engine computer notices, and it keeps count for each cylinder. P0303 — "Cylinder 3 Misfire Detected," printed by Toyota as "P030300 – Cylinder 3 Misfire Detected," by Honda as "No. 3 cylinder misfire detected," and by Mazda as "P0303:00" — means cylinder 3 crossed the threshold. It names a cylinder. It does not name a spark plug, a coil, an injector, a gasket or a piston. P0300 is the random or multiple-cylinder version, and P0301 to P0308 are the same code for the other cylinders.

We found 745 manufacturer documents — 595 from our search of NHTSA's index and 150 that a second, independent search found — that name P0303, a range or wildcard that contains it, a misfire on cylinder 3 or a companion code for that cylinder: service bulletins, special service messages, warranty extensions, dealer messages, preliminary information and owner letters from Ford, Honda, Acura, Stellantis, GM, Hyundai, Kia, Toyota, Lexus, Mazda, Audi, Volkswagen, BMW, MINI, Land Rover, Jaguar, Infiniti, Nissan, Mercedes-Benz, Subaru and others. PulsCar went through them all in full, comparing near-identical copies sentence by sentence against a copy read in full; 680 turned out to be relevant, and 461 of those print P0303 itself in some form. In almost every one, P0303 is one line of the full misfire family. Only nine document families single out a misfire on cylinder 3, naming it with one or two other cylinders or as part of a bank — and in none of them is the fix a coil or plug for cylinder 3 alone. The repairs are software, a new engine computer, a valve timing solenoid, an exhaust manifold, an air cleaner pipe, a crank sensor rotor, and piston rings with a full set of plugs or a new block.

The federal complaint file tells a more expensive story. PulsCar went through all 1,301 complaints in NHTSA's file from 2015 to September 2026 that name P0303 in any spelling, name a code range that includes it, or describe a misfire on cylinder 3 in words; 1,029 came from our first search and 272 from a second, independent one. Each complaint was sorted twice, independently, by the same written rules. 1,286 were about a cylinder-3 misfire on the owner's car. In 562 the narrative ends with coolant in a cylinder, a failed head gasket or a cracked block or head — 430 of them on a Ford or Lincoln. In 472, plugs, coils or other parts were replaced for the misfire and it continued or the real cause turned up later.

By the end you will know which of five routes your P0303 is on, what each costs in 2026, which bulletin or coverage we read applies to your vehicle, and the one test that should come before the second coil.

Claims marked 🟢 rest on a document listed in the Sources section, read in full. Claims marked ⚪ are shop-price estimates carried from our repair guides. Owner-reported figures are what people told NHTSA, published with ODI numbers, and every complaint count here comes from the 1,301 complaints sorted twice and published.

I built PulsCar after a $380 "full diagnostic" in Phuket in 2025 led to roughly $6,000 over six months across several shops (the story is on the About page). P0303 is that pattern at its most expensive: a code that points at a cylinder, a coil that is cheap to try, and on some engines a head gasket or a block that nobody checks until the third visit. Every claim below that rests on a document names it.

What P0303 says: cylinder 3 misfired, not why

What the computer counts. The engine computer watches how each cylinder's combustion stroke turns the crankshaft. A cylinder that fires weakly or not at all shows up in that pattern, and the computer charges the event to the cylinder it believes was firing. Enough events in a window sets P0303. A heavy misfire flashes the check engine light.

What it does not know. Why the cylinder misfired. A tired plug, a failing coil, a clogged injector, a leaking valve, oil on the plug from worn rings, or coolant seeping past a gasket all look the same to the misfire counter. So does a vibration that is not a misfire at all: 🟢 Ford's special service message 53869 says that on some 2021-2024 Bronco 2.3 models "The driveline torsional harmonics/vibrations are incorrectly identified by the misfire monitor as an engine misfire."

Which cylinder it blames. Usually the right one. Not always: 🟢 Ford's SSM 52455 for 2023-2025 6.8 and 7.3 gas engines warns of "incorrect cylinder to DTC mapping within the PCM. This means the DTCs listed may set against the incorrect cylinder," and tells the technician to find the real one with a cylinder power balance test. 🟢 Stellantis's 18-161-22 for the 2019 Cherokee 2.0 turbo says "Injector performance faults for cylinders 2 - 4 map to DTC for incorrect cylinders" — an injector circuit code, not P0303, but the same lesson.

What happens when it sets. A misfiring cylinder sends unburned fuel into the exhaust. The car may shake at idle, stumble under load or lose power, and some engines shut off fuel to the cylinder they blame. That is why a flashing light means stop.

First: is cylinder 3 alone, or part of a pair, a bank or the whole family?

This decides which documents apply. Write down every code, not just P0303.

Why the pattern matters. When cylinder 3 misfires alongside a neighbor, the makers point at something the two cylinders share: a bank, an intake or exhaust path, a solenoid, or the computer. When it misfires alone, the fault is usually in that cylinder — and on the engines in Route 5, that includes coolant coming through the gasket or the block right at cylinder 3. In the complaints, 141 of the 562 coolant cases also name a second cylinder.

The P0303 family, and what the documents actually print

Search traps. A search for the literal string "P0303" misses every document that prints only a range or a wildcard, which is why ours covered those forms too. It also finds false friends: 🟢 four Infiniti documents use "P0303" as an internal campaign ID for a 2007-2008 FX speedometer and odometer correction, and several Jeep bulletins mention "Cylinder 3 Injector Circuit Performance" — P02F0, an injector circuit code, not a misfire.

The maker atlas: who wrote about a cylinder-3 misfire, and what they blamed

Ford: coolant in the cylinder, then ignition. 🟢 The 1.5 EcoBoost chain from 19-2375 to 22-2322 and program 21N12, and the 2.0 EcoBoost chain from SSM 47204 and 19-2172 to 22-2229, treat misfire codes P0301 to P0304 with low coolant or white smoke as possible "coolant intrusion into the cylinder" and end in a new short block or long block. 🟢 22-2017 and 24-2257 tie P0301, P0302 and P0303 on 2021 F-150 PowerBoost models to the right air cleaner outlet pipe. 🟢 Water in the plug wells on Rangers, coils with a bad date code on 2024-2025 EcoBoosts, and scored cylinder walls behind damaged plugs fill out the list.

Honda and Acura: rings, gaskets, injectors, carbon, software. 🟢 13-081 and its siblings (2008-2013 Accord, Crosstour, Odyssey, Pilot), and the 2025-2026 bulletins 25-060, 25-061, 26-001 and 26-002 repair piston rings, and treat P0301, P0302 or P0303 as cylinders 1 to 3. 🟢 The August 2026 head gasket extensions, announced in dealer message AEBM08262026901, list misfire codes P0300 to P0304 among the symptoms. 🟢 20-100 and 21-010 cover injectors on V6 Odysseys, Pilots and Ridgelines; 21-007 cleans carbon on the Fit; the 1.5 turbo Civic and CR-V bulletins update software and, in some cases, replace camshafts.

Stellantis: software flashes, plugs and cam wear. 🟢 Dozens of flash bulletins list P0300 to P0306 or write the family as P030X. 🟢 09-013-20 REV. A replaces all six plugs on 3.6 engines built in a late-2020 window "if one DTC is found." 🟢 09-011-25 describes worn intake cam lobes and rocker sliders on 3.6 engines from 2018 to 2025, Pacifica included. 🟢 09-017-26 REV. A traces misfires on 2026-2027 Grand Cherokee 2.0 Hurricane engines to a missing umbrella valve seal and oil loss.

Toyota, Lexus, Mazda, Hyundai, Kia, GM and the Europeans. 🟢 Toyota's T-SB-0010-24 prints "P030300 – Cylinder 3 Misfire Detected" for cold-soak misfires on A25A and M20A engines and replaces the exhaust-side lash adjusters. 🟢 Lexus traces companion misfires on cylinders 3 and 6 on the RX350 to the crank sensor rotor, and misfires on 2.0 turbo engines to worn valve guides. 🟢 Mazda's 01-010/18 blames a sticking exhaust manifold valve on early CX-9s. 🟢 Hyundai and Kia fix misfire families with computer logic updates and spark plugs. 🟢 GM's lifter bulletins cover V8 trucks. 🟢 Audi, BMW, MINI, Volkswagen and Infiniti fix several cylinder-specific patterns with software or a new engine computer. 🟢 Land Rover and Jaguar replace variable valve timing solenoids, fitting only parts made on or after 23 August 2018.

The 10-minute P0303 check

1. Read every code and the freeze frame (2 minutes). P0303 alone, or with P0302, P0306, P0300 or the rest of the family? A coolant temperature code, P0299, a camshaft code or an air-fuel code next to it changes the route. Write down the engine temperature and speed in the freeze frame, the snapshot the computer saved when the code set.

2. Watch the light (1 minute). Steady, or flashing? Flashing means a heavy misfire now; park the car.

3. Look at the coolant (2 minutes, engine cold). Is the reservoir below the line, and has it been topped up before? Coolant that keeps dropping with no puddle, a sweet smell or white smoke at a cold start points at Route 5.

4. Check the oil (2 minutes). Level and color. Oil that goes down fast points at rings or valve seals (Route 4); milky oil points at coolant.

5. Swap the coil (3 minutes, where the coils are easy to reach). Move the cylinder 3 coil to cylinder 2 or 4, clear the code and drive. 🟢 Honda's own request for parts on 2008 Civic CNG misfires told dealers they "Must verify misfire by swapping coils to confirm that the issue follows the coil." If the misfire moves, the coil is guilty. If it stays on cylinder 3, stop buying ignition parts.

Eight P0303 situations, and which is yours

"P0303 on a 1.5 or 2.0 EcoBoost — a 2014-2019 Fusion, a 2017-2019 Escape, MKC or MKZ, or a 2015-2018 Edge — with coolant going down." Coolant intrusion. → Route 5.

"P0303 on a Honda Accord, Civic or CR-V from 2016 on, with coolant loss or white smoke." Head gasket. → Route 5.

"P0303, often with P0301, P0302 and P0304, on a 2013-2017 Odyssey or 2013-2015 Pilot, with oily plugs." Piston rings. → Route 4.

"P0303 and a neighbor on a Mazda CX-9, a MINI, an Audi A8, a BMW V8, an F-150 PowerBoost, a Q50 or Q60, or an RX350." A shared cause or software. → Routes 1 and 3.

"The misfire followed the coil when you swapped it." Ignition. → Route 2.

"P0303 at a cold start in freezing weather on a 2018 or newer Camry, RAV4, Corolla or Avalon four-cylinder." Lash adjusters. → Route 4.

"P0303 after new plugs and a coil, still there." Not ignition. Compression, leak-down (air fed into the cylinder to hear where it escapes) and a borescope (a camera through the plug hole) before anything else. → Routes 3 to 5.

"P0303 once, and the light went out on its own." Nothing to swap yet: a swap test proves nothing until the misfire returns. Write down the date, mileage, weather and whether the engine was cold, check the coolant and oil cold, and read the freeze frame if the code is still stored. The makers confirm a code before repairing it. → Watch; Route 2 if it returns.

The P0303 price ladder, from the bottom up

The first six lines decide whether the rest is needed. The ⚪ figures come from our P0301 guide, which carries the same estimates for any single-cylinder misfire; the owner figures are listed with ODI numbers in the published file. The engine figures leave out one $375 contribution a Ford dealership offered an Escape owner toward the costs.

How much does it cost to fix P0303 in 2026, and when is a coil the wrong purchase? Our repair guides carry spark plugs at $80 to $400, an ignition coil at $150 to $400 per coil and a compression or leak-down test at $100 to $300. In PulsCar's reading of 1,301 federal complaints, owners report $167 to $4,376 for ignition work, median $700; $1,319 to $11,000 for head gasket and coolant repairs, median $5,000; and $2,000 to $25,000 for engines, median $8,396.50, most of them quotes. A coil is the wrong purchase when a swap test leaves the misfire on cylinder 3, when coolant keeps dropping with no leak on a Ford 1.5 or 2.0 EcoBoost or a Honda 1.5 turbo, and when the plugs come out wet with oil on a 2013-2017 Odyssey or 2013-2015 Pilot, where Honda's own bulletins replace piston rings.

The five P0303 routes, cheapest first

Route 1 · Software, false counts and the computer — $0 under warranty

What it is. Nothing is wrong inside cylinder 3. The engine computer counts misfires it should not, labels them to the wrong cylinder, or runs software settings that let the engine stumble. The fix is a reprogram, occasionally a new computer, and several makers say in writing not to replace parts first.

What the documents say.

🟢 BMW SI B12 10 16, 7 Series, 6 Series and 5 Series Gran Turismo models with the N63T V8 produced to 7/2013. "Erroneous misfire faults may be stored for cylinders 3 and 6." It happens "after driving for several hours at constant highway speeds with light throttle"; the cause is "DME software (plausibility check error)" and the repair is to reprogram the car.

🟢 MINI SI M12 11 14, F56 Cooper S produced to 7/2014. A "Drive Moderately" message with misfire faults stored only as a pair — cylinders 1 and 4, or cylinders 2 and 3 — from "Unfavorable DME software." Any other combination, or a single cylinder, gets the normal test plan.

🟢 Audi 2060491/1, 2019 A8 3.0 TFSI. At least two of P030100, P030200 and P030300 at the same time, from fuel vapor purged into bank 1 in high outside temperatures: "This occurs only on bank 1 because of a too rich mixture." The fix is engine computer software, and the bulletin is explicit: "For a single cylinder misfire DTC this bulletin does not apply, continue diagnosis outside of this TSB." 🟢 Audi's 2058309/5 for 2019-2020 A6 and Q3 2.0 TFSI engines blames "Deviating adaptation values during the break in period of the engine" and says "Do not replace any components to correct misfire DTC’s, idle quality, and drivability concerns."

🟢 Infiniti ITB21-009, 2021 Q50 and Q60. One trigger is P0300 with "misfire events on cylinder 3 and cylinder 6 only." The repair is a new engine computer, programmed twice.

🟢 Volkswagen 01-21-02, 2018, 2020 and 2021 Atlas and 2020-2021 Atlas Cross Sport 2.0T. P0300 to P0304 each listed, fixed by software for "better combustion stability during catalyst heating and engine warmup" — and "DO NOT diagnose or replace any components for the above fault(s) before performing the update." 🟢 Hyundai 20-01-008H, 2018-2019 Elantra 2.0, and Kia 165, 2017 Forte 2.0, update the engine computer's misfire logic — with Kia's warning that "This reflash will not address a faulty component."

What the owners report. Software is rare in the complaints: 18 of 1,286 name a computer, wiring, a sensor, a solenoid or a recall repair as the cause. A 2018 Elantra owner describes three rounds of coils and a dealer that refused the software update because the VIN was not in the campaign.

The cheap cause that gets skipped. The software level. A dealer can compare it with the latest in minutes, and on the vehicles above it is the repair.

At the shop — say this: "Is there a software update or bulletin for misfire codes on my VIN — and does it say not to replace parts first? If P0303 came with a second cylinder, which bulletin covers that pair?"

Route 2 · The coil, the plug and water in the well — $80 to $400 when the swap test convicts them

What it is. The spark on cylinder 3 is weak or missing: a worn or cracked plug, a failing coil, a boot that leaks, or water sitting in the plug well. This is the route most quotes start with, and the only one where replacing the cylinder 3 part is the fix.

What the documents say.

🟢 Ford 21-2147, 2019-2021 Ranger. "This may be due to water build up in the spark plug well(s) which can lead to signs of corrosion on ignition system components" — the engine appearance cover was missing. The bulletin fixes the misfire "per normal diagnostics" and then installs the cover so the water stays out.

🟢 Ford 26-2210, EcoBoost Bronco, Bronco Sport, Escape, Explorer, Maverick, Mustang, Ranger and Corsair models built 1 June to 31 December 2024. "Inspect the date code on the ignition coil for the cylinder setting the misfire DTC." Only a coil built from 1 April through 31 October 2024 is replaced — and only that one.

🟢 Stellantis 09-013-20 REV. A, 2020-2021 Pacifica, Durango, Grand Cherokee, Wrangler, Gladiator and Ram 1500 3.6 engines built in a late-2020 window. "Due to a known manufacturing issue with the original spark plugs, all six spark plugs must be replaced for this Repair Procedure if one DTC is found." 🟢 Kia 186, 2018 Forte and Rio: plugs whose porcelain cracked "during manufacturing," all four replaced "whether or not the MIL is ON." 🟢 Hyundai 18-01-017-1, 2018 Accent 1.6: all four plugs inspected and replaced, and if ceramic is missing, "DO NOT START ENGINE."

🟢 Ford SSM 52419 and 24-2384, 2023-2025 Escape, Corsair, Nautilus, Explorer and 2024 Mustang EcoBoosts. A damaged plug is a clue, not the end: "If any spark plugs appear to be damaged, use a borescope to inspect the condition of the cylinder walls." Scored walls mean a long block; undamaged plugs mean "replacement of the spark plugs is not necessary."

What the owners report. Only 32 of 1,286 complaints end with ignition as the stated fix, and 23 ignition figures run from $167 to $4,376. A 2013 Odyssey owner paid $166.75 for a cylinder 3 coil and plug at another shop; a 2015 Malibu owner changed the plug, then paid $170 at a dealer that found the coil. Far more often the ignition part came first and the misfire stayed: 472 complaints describe parts replaced before the real cause turned up.

The cheap cause that gets skipped. The swap test and a look at the old plug. A plug wet with coolant or oil, or cracked, tells a different story from a worn one.

Fix it yourself — what to check. Where the coils sit on top of the engine, swap the cylinder 3 coil with a neighbor, clear the code and drive. Look for water or oil in the plug well. Pull the plug if you have the tools and note its color and whether it is wet. Plugs on transverse V6 engines, where the rear bank sits under the intake, are a shop job.

At the shop — say this: "Did the misfire follow the coil when you swapped it? What did the cylinder 3 plug look like — wet, oily, cracked? If it stayed on 3, I would like a compression test before any more ignition parts."

Route 3 · Air, fuel and the parts two cylinders share — $0 to about $4,000

What it is. Cylinder 3 gets the wrong mixture: a clogged or leaking injector, carbon on the intake valve, a restricted intake or exhaust path, or a part that two cylinders share — which is why so many of these documents name cylinder 3 with a neighbor.

What the documents say.

🟢 Mazda 01-010/18, 2016-2017 CX-9 with VINs lower than JM3TC****135222, built before 27 December 2016.** "P0303:00 - Cylinder No.3 misfire detected," with P0302, during acceleration with the light flashing: "This concern may be caused if the exhaust manifold variable valve shaft (1) is out of alignment and/or the exhaust manifold variable valve housing (2) is out of shape." The valve sticks closed when hot; the fix is a modified exhaust manifold, 4.2 to 4.3 hours printed.

🟢 Ford 22-2017, superseded by 24-2257, 2021 F-150 3.5 PowerBoost built on or before 30 September 2021. Reduced power with "DTC P0299, P0301, P0302 and/or P0303": "This may be due to a restriction in the right air cleaner outlet pipe." The pipe is replaced, and the right turbocharger too if it is damaged. The bulletin pairs the three codes with right-side parts; it does not itself say which bank they are on.

🟢 Land Rover SSM74161 and Jaguar SSM74160, 2.0 four-cylinder engines. "P0303-00 and P0302-00" with camshaft codes and no drivability concern: "a number of Variable Valve Timing Solenoids have not been manufactured in accordance with the required specification." A replacement made "prior to 180823xxxxx (23rd August 2018)" must not be fitted.

🟢 Lexus L-SB-0008-21, 2018-2021 RX350. Companion misfires in pairs, among them "P030300 and P030600 (Cylinders 3 and 6 Misfires Detected)." If the freeze frame's all-cylinder misfire count is four or less, the repair is a new crank sensor rotor and software — not a coil or an injector.

🟢 Honda 20-100 (2016-2017 Pilot, 2017 Ridgeline, 2018 Odyssey) and its companion 21-010. Misfire codes written as a range or "P030x," from injector wear: "American Honda is extending the warranty on these repairs to 10 years from the original date of purchase or 150,000 miles, whichever comes first." 🟢 Honda 21-007, 2015-2020 Fit: "Carbon buildup on the intake valves may be affecting combustion" — and "Do not replace the fuel injectors; follow the steps in the INSPECTION PROCEDURE first."

What the owners report. 67 complaints end with a fuel or air cause, led by the CR-V and the Tucson with 12 each. A 2016 Fit owner was quoted $2,300 for all the fuel injectors instead of the one on cylinder 3. A 2019 Pilot owner, whose dealer said the injector extension did not cover the car, was quoted $479 for parts and $895 for labor.

The cheap cause that gets skipped. The second code. P0303 with P0302 on a CX-9, a Land Rover or a MINI, or with P0301 and P0302 on a PowerBoost, points to something shared, and the bulletin names it.

At the shop — say this: "Which other misfire codes are stored with P0303, and is there a bulletin for that combination on my VIN? Before an injector, can you check whether the injector warranty extension or the carbon cleaning bulletin applies?"

Route 4 · Rings, valves and lifters — $408 to $25,000 in owner reports

What it is. Cylinder 3 cannot hold compression or keeps fouling its plug: piston rings stuck with sludge, worn valve guides, a collapsed lifter or a worn cam lobe, lash adjusters that misbehave when cold. A new plug may clear the code for weeks. A compression or leak-down test tells you.

What the documents say.

🟢 Honda 25-061 and 26-001, 2013-2017 Odyssey; 25-060 and 26-002, 2013-2015 Pilot. "The piston ring function deteriorates due to ring wear and sticking from sludge. Oil from the crankcase adheres to the spark plug leading to carbon fouling and misfire." The repair is keyed to the code: "DTC P0301, P0302, or P0303" means cleaning pistons and replacing rings on cylinders 1 to 3; P0304 adds cylinder 4; a failed cylinder inspection means a new block. The 2025 bulletins covered repairs "to January 31, 2026"; the renumbered 2026 bulletins restate 10 years from the original date of purchase or 150,000 miles. 🟢 The older 13-078 to 13-082 family for 2008-2013 models, from the Soto class action, did the same under an 8-year extension.

🟢 Toyota T-SB-0010-24 Rev2, 2018-2024 Camry, 2019-2025 RAV4 and Corolla, 2022-2025 Corolla Cross and 2021-2022 Avalon. "P030300 – Cylinder 3 Misfire Detected" at a cold start "with engine coolant temperatures between 14°F – 41°F": compression is checked, then "ALL the exhaust side hydraulic lash adjusters" are replaced. 🟢 Lexus L-SB-0007-21 Rev2, 2.0 turbo IS, RC, GS and NX models: "This may be caused by cylinder compression pressure drop due to improper exhaust valve sealing from worn valve guides," and the repair is a cylinder head.

🟢 Stellantis 09-011-25, 3.6 engines in 2018-2025 Pacifica, Wrangler and Durango, 2018-2025 Grand Cherokee, 2019-2025 Ram 1500, 2020-2025 Gladiator and 2022-2025 ProMaster, built before mid to late 2024. Worn intake cam lobes and rocker sliders, "within 10,000-60,000 miles" — and "There is a special service kit for this type of repair which should be used instead of replacing the complete engine/long block." 🟢 GM 23-NA-043 replaces collapsed lifters on 2020-2021 5.3 and 6.2 V8s. 🟢 Ford 18-2237 replaces the cylinder heads on 2016-2017 F-150 2.7 EcoBoosts that use oil. 🟢 Stellantis 09-017-26 REV. A, 2026-2027 Grand Cherokee 2.0 Hurricane: a missing umbrella valve seal lets the engine burn oil — but "Vehicles exhibiting misfire DTCs alone without low oil level are not candidates for this procedure."

What the owners report. 291 complaints end with a mechanical cause, led by the Odyssey with 35, then the Soul with 15 and the Ram 1500 and Escape with 13 each. Of the 77 Odyssey and Pilot complaints, 47 are mechanical; a 2016 Odyssey owner's dealer said "oil is leaking past the piston rings and fouling the #3 spark plug causing misfiring," and a 2013 owner was told "the spark plugs are being fouled with oil." A 2022 RAV4 owner paid $2,549.65 for the lash adjuster repair at 163,000 miles, past the 60,000-mile powertrain warranty. Engine and valvetrain figures for Odysseys and Pilots run from $2,686.36 to $12,500; across all mechanical complaints, 68 engine and valvetrain figures run from $2,000 to $25,000, median $7,000.

The cheap cause that gets skipped. The compression and leak-down test, before the second plug and long before an engine quote.

Fix it yourself — what to keep. The old plugs, photographed; the oil level at every fill-up; and the dates and mileage of every misfire. Honda's ring bulletins start from which codes are stored and whether the plugs are fouled.

At the shop — say this: "What are the compression and leak-down numbers for cylinder 3 and its neighbors? Is there a ring, lifter, lash adjuster or valve guide bulletin for my engine, and does a warranty extension cover it?"

Route 5 · Coolant in the cylinder — the head gasket or the block, $1,319 to $16,736

What it is. Coolant seeps into cylinder 3 through a failing head gasket, a cracked head or a porous or cracked block. It fouls the plug, sets P0303, and slowly empties the reservoir. A new coil or plug clears the code for a while. This is the most common ending in the complaint file.

What the documents say.

🟢 Ford 1.5 EcoBoost: 2014-2019 Fusion built on or before 10 June 2019 and 2017-2019 Escape built on or before 8 April 2019. Low coolant, white smoke or a rough run with P0300 or the range "P0301-P0304": "This may be due to coolant intrusion into the cylinder." The test: pressurize the cooling system to 138 kPa (20 psi) for 5 hours; a drop of more than 4 psi means the plugs come out and the cylinders are inspected; coolant in any cylinder means a new short block with a new head gasket, 19.5 to 21.5 labor hours printed in 22-2322. The replacement is "a cross-drilled design," where the original was a saw-cut block, so a head gasket alone is not Ford's repair.

🟢 Ford 2.0 EcoBoost: 2015-2018 Edge, 2017-2019 Escape, Fusion, MKC and MKZ, by build date. The same test and a new long block, 13 to 15.5 hours printed in 22-2229. The earlier 19-2172 says "this TSB does not require obtaining Prior Approval or completion of a Cost Cap."

🟢 Ford program 21N12, June 2022: "This program provides a no-cost, one-time repair (if needed) to the 1.5L short block, due to coolant intrusion to the cylinder bores, for 7 years of service or 84,000 miles from the warranty start date of the vehicle, whichever occurs first." Vehicles already past the limits were covered only "through November 30, 2022."

🟢 Honda and Acura, August 2026. "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." The dealer message covers certain "2018-2026 Accord, 2018-2026 Accord Hybrid, 2016-2026 Civic, 2025-2026 Civic Hybrid, 2017-2026 CR-V and 2020-2026 CR-V Hybrid vehicles," and Acura's covers 2025-2026 ADX and 2023-2026 Integra. Coverage runs "10 years from the original date of purchase or 150,000 miles, whichever comes first"; the oldest 1.5 turbos — 2016-2017 Civic and 2017 CR-V — get coverage "to May 31, 2027, regardless of time in service or mileage." The test: pressurize to 18 psi, warm the engine, pull all four plugs and borescope "all cylinders for coolant entering at the head gasket." Customer letters were due to start in early October 2026. 🟢 Two years earlier, Honda was already asking dealers for such cars: a September 2024 dealer message requested parts from 2017-2022 CR-V 1.5, 2018-2022 Accord hybrid and 2020-2022 CR-V hybrid cars with P030X codes where a "Head Gasket coolant leak to cylinder has been confirmed by performing borescope inspection or pressure test."

🟢 What we did not find. No document in our set addresses head gaskets on the 2017-2020 Chrysler Pacifica 3.6. Chrysler's X56 extension (09-002-14 REV. B), read for our P0302 study, covers the left cylinder head on 2011-2013 3.6 models other than the Pacifica and tells technicians to "Perform a cylinder leakage test on cylinders 2, 4 and 6" — not cylinder 3.

What the owners report. 562 complaints were sorted here. Ford and Lincoln account for 430: the Escape 194, the Edge 103, the Fusion 82, the Mustang 17 and the MKC 16, with the 2017 model year alone at 174. The Pacifica follows with 51, and the Honda Accord with 42, 30 of them 2018 models. A 2017 Escape owner's dealer "FOUND COOLANT IN CYLINDER 3" after a plug change and quoted about $8,300 for a long block; a 2018 Accord owner quotes the shop's notes: "Found coolant entering cylinder 3." Across the coolant complaints, 133 engine and head gasket figures run from $1,319 to $16,735.60, median $8,036.29, most of them quotes. On Fords and Lincolns alone, 103 of those figures run from $3,500 to $16,735.60, median $8,500, 82 of them quotes; on the 1.5 turbo Accord, Civic and CR-V, 20 figures from $2,700 to $11,000, median $5,750; on the Pacifica, 9 figures from $1,319 to $16,000.

The cheap cause that gets skipped. A cold coolant level check and the pressure test, before the plug. On the Fords and Hondas above, the bulletin describes exactly how.

Fix it yourself — what to watch. Mark the coolant level on the reservoir with the engine cold and photograph it; if it has dropped since the last top-up, that is your answer, so do not drive a week to measure it. Note any white smoke at start-up and any sweet smell. Keep every receipt for coolant, plugs and coils; they show the story in order.

At the shop — say this: "Before another plug or coil, please pressure test the cooling system as the bulletin describes and borescope cylinder 3 for coolant. Which bulletin or warranty extension applies to my VIN, and what did the borescope show? Please put both results on the repair order."

The coverage file: which programs are still running in September 2026

The status column is our own calculation from the terms printed in each document, as of September 2026 — not a statement by the manufacturer. Check the exact VIN.

How we computed it. A 10-year term that starts at purchase is still running in September 2026 only for a car first bought after September 2016, and only under the mileage cap. For the 2013-2017 Odyssey that means mostly 2017 models and late-sold 2016s; for the 2013-2015 Pilot, almost none. Ford's 21N12 counts 7 years from each vehicle's warranty start date, and the last affected vehicles were built in June 2019, so it is running only for a vehicle whose warranty started after late September 2019 and that has not reached 84,000 miles. Honda's dealer message also promises "a 6-month grace period from the date of customer notification" for cars that are no longer eligible because of their age. The Honda May 31, 2027 bulletins replaced first versions that also had a 150,000-mile cap; the revised versions say "regardless of time in service or mileage."

Two details that decide claims. First, Honda's head gasket bulletins require an all-code printout and a borescope image with the claim, and replacing the head or the short block needs Honda's approval — ask for both results on paper. Second, the Ford 1.5 and 2.0 bulletins are repair procedures, not coverage; out of warranty, the bulletin tells the shop how to test, and the owner pays.

What 1,301 complaints about a cylinder-3 misfire show

PulsCar went through every complaint in NHTSA's file from 2015 to 21 September 2026 that names P0303 in the spellings we searched (P0303, PO303, P 0303, P030300, P0303-00), a code range that includes it, or a misfire on cylinder 3 in words: 1,301 complaints. The first search found 1,029. Before writing, a second, independent search of the same file looked for what the first had missed — P303 and 0303 written without the zero or the P, "P0300-P0306" and "PO300-303", cylinder lists such as "cylinders 2 and 3" or "1-3", and "a code for cylinder 3" without a number — and found 272 more. Every complaint was sorted twice, independently, by written rules fixed before the sorting began. The two sortings matched on the category for 1,185 of 1,301 (91%), and on whether the car stalled or lost power for 1,266 (97%). Every disagreement was settled by the written rules, and a final check of the matching sortings against those rules changed four more; the published file carries both sortings, the final one and which search found each complaint.

The file belongs to Ford. Ford accounts for 553 of the 1,286 relevant complaints and Lincoln for 30. Honda follows with 209, Hyundai with 100, Chrysler with 87 and Kia with 83. By model: the Escape 255, the Edge 133, the Fusion 105, the Pacifica 77, the Accord 73, the Odyssey 53, the CR-V 32, the Soul 29 and the Tucson 27.

Ignition is rarely the last word. Only 32 complaints end with a plug or coil that fixed it. In 472, parts were replaced for the misfire and it continued or the cause turned up later — 188 of them in the coolant group.

The misfires are not gentle. 468 complaints describe a stall, limp mode or a loss of power that left the driver unable to keep up with traffic.

It is getting more frequent. By year received: 14 in 2015, 16 in 2016, 22 in 2017, 26 in 2018, 49 in 2019, 73 in 2020, 49 in 2021, 98 in 2022, 191 in 2023, 258 in 2024, 262 in 2025 and 228 in 2026 to 21 September. The median model year is 2017, and of the 415 complaints that give a plausible mileage, the median is 90,000 miles.

Counting complaints, not cars. Some owners filed more than once, and in 60 of the 1,286 the narrative does not confirm cylinder 3 on the owner's car — P0303 appears only inside a range quoted from a bulletin, or the car's own code named another cylinder. Every figure here counts complaints. Nothing here is a failure rate.

What do 1,301 federal complaints about a cylinder 3 misfire show, and why do Ford EcoBoosts dominate them? In PulsCar's reading of every complaint that names P0303, a code range containing it or a cylinder 3 misfire in words, each complaint was sorted twice, independently, and the two sortings matched on the category for 1,185 of 1,301 (91%). Of the 1,286 relevant complaints, 562 end with coolant in a cylinder, a failed head gasket or a cracked block or head, and Ford and Lincoln account for 430 of those — mostly 1.5 and 2.0 EcoBoost Escapes, Edges and Fusions, the engines Ford's coolant intrusion bulletins describe. Another 291 end with a mechanical cause, led by Honda Odysseys, and only 32 with a plug or coil that stayed fixed. In 472 complaints, parts were replaced before the real cause was found.

What owners say they paid

We collected every dollar figure for a diagnosis, an ignition, fuel or air part, a cooling system or head gasket repair, a valvetrain repair, an engine or another repair tied to the misfire in the 1,301 complaints — 303 figures, 183 of them quotes and 88 described as paid — leaving out rentals, towing, loans, vehicle prices and unrelated repairs, and the full list with ODI numbers and the inclusion rule is published. By purpose:

A diagnosis. 20 figures from $77, paid at an independent shop for a 2018 Odyssey, to $1,084, quoted by a dealer for a diagnostic inspection on a 2018 EcoSport; median $177. A Lincoln MKC owner paid $205 at a dealer, which found coolant leaking into the engine, and $177 at another shop, which placed it in cylinder 3.

Ignition. 23 figures, median $700: $166.75 for a cylinder 3 coil and plug on a 2013 Odyssey, $780.25 billed for a coil pack, plugs and wires on a 2005 Freestar, $2,700 quoted by a dealer for a valve cover seal and oil-soaked plugs and coils on a 2020 Pacifica plug-in hybrid, and $4,376.35 quoted for ignition parts on a 2021 E-350 misfiring on "almost every cylinder."

Fuel. 21 figures, median $1,300: $147 for a purge valve on a 2016 Civic, $1,495.53 for four injectors on a 2018 Accord misfiring on cylinders 2 and 3, $2,300 quoted for all the injectors on a 2016 Fit.

Head gaskets and coolant. 30 figures from $1,319 to $11,000, median $5,000: $2,700 billed for a head gasket on a 2018 Civic, $4,600 quoted for a Pacifica, $7,400 quoted for a 2019 Accord's head gasket with a hairline crack at cylinder 3.

Rings, valves and lifters. 22 figures, median $4,200: $3,200 paid for piston rings on a 2014 Odyssey, $4,000 for a ring job on a 2012 Odyssey, $7,545.72 quoted for a cylinder head on a 2022 CLA 250, $10,000 to $12,000 quoted after a collapsed lifter on a 2019 Silverado.

An engine. 164 figures, 131 of them quotes, median $8,396.50. On Fords and Lincolns, 72 of the 115 engine figures fall between $7,000 and $10,000: $5,004.12 paid for a remanufactured block on a 2016 Edge, $7,800 paid for an engine and turbo on a 2017 Escape, $16,735.60 quoted for a 2019 MKC. Eighteen owners report paying for an engine, from $2,686.36 to $10,500, median $7,100.

Why P0303 comes back after a new coil

Because the coil was not the fault. In 472 complaints, parts were replaced for the misfire and it continued or the real cause turned up later. A 2017 Pacifica owner's mechanic "said it was the 3rd cylinder. Had that replaced, but the vehicle continued to have problems" — then the head gasket. The documents name the reasons: 🟢 coolant through the gasket or the block (Ford, Honda), 🟢 oil past stuck rings (Honda), 🟢 worn valve guides, lash adjusters, lifters and cam lobes (Lexus, Toyota, GM, Stellantis), 🟢 injectors and carbon (Honda), 🟢 a stuck exhaust valve or a restricted intake shared with a neighbor (Mazda, Ford), and 🟢 software (Audi, BMW, MINI, Volkswagen, Hyundai, Kia).

Because the code named the wrong cylinder. 🟢 Ford's SSM 52455 and Stellantis's 18-161-22 both describe software that set codes against the wrong cylinder. A cylinder power balance test finds the real one.

Because the misfire moved. One 2017 F-150 owner writes that the scanner showed "possible misfire.... cylinder 1 and 4.... last month it was cylinder 3." A misfire that wanders from cylinder to cylinder points at something they share.

Why does P0303 keep coming back after the coil and plug on cylinder 3 are replaced? In PulsCar's reading of 1,301 federal complaints and the manufacturer documents on cylinder 3 misfires, 472 complaints describe parts replaced for the misfire before the real cause was found, and only 32 end with a plug or coil that stayed fixed. The documents explain why. Ford's 1.5 and 2.0 EcoBoost bulletins trace misfire codes with low coolant to coolant leaking into the cylinder and replace the block; Honda's 2026 head gasket bulletins borescope every cylinder for coolant; Honda's Odyssey and Pilot bulletins replace piston rings that let oil foul the plug. Toyota, Stellantis and GM name lash adjusters, worn cam lobes and collapsed lifters, and Ford and Stellantis software that blamed the wrong cylinder. Swap the coil once, then test compression.

Can you drive with P0303?

With a steady light and a car that runs normally: gently, for a short time. Book the diagnosis this week, check the coolant and oil levels cold, and keep an eye on the temperature gauge.

Not with a flashing light, hard shaking or power loss. In the complaint file, 468 of 1,286 describe a stall, limp mode or a loss of power. A 2016 Escape shuddered and hesitated at 50 mph; a month after a new coil, the dealer found cylinders 2 and 3 misfiring and coolant intrusion.

Not with coolant disappearing. An engine that burns coolant can overheat, and on the Ford and Honda engines above the bulletins end in a new block or head. Have it towed and ask for the pressure test.

Should you buy a used car with a P0303 history?

It depends on what fixed it. A receipt for a coil that passed the swap test, a software update or a bulletin repair is a closed file. A cylinder 3 plug and coil replaced twice is an open one.

On a Ford 1.5 or 2.0 EcoBoost, a Honda 1.5 turbo or a 2013-2017 Odyssey, ask for three things. The coolant top-up history and any pressure test result; which bulletin or program was done, with the repair order (Ford's 21N12 moves with the car); and the original purchase date, because the Honda terms count from there. Then run the VIN at nhtsa.gov/recalls and ask a dealer about open campaigns and extensions.

Clearing P0303 before an inspection

Clearing the code does not clear the cause. Erasing codes resets the readiness monitors, which need days of mixed driving to complete, and a cylinder that still misfires will set P0303 again. A car presented with too many incomplete monitors can be turned away or failed.

What works instead. Fix the route, clear the code, and drive normally for several days. If the coolant is still going down, the next inspection will not be the problem.

What a shop actually does with a cylinder-3 misfire, checkpoint by checkpoint

Checkpoint 1: every code and the freeze frame — is cylinder 3 alone, or with a neighbor, a bank or the family?

Checkpoint 2: bulletins, software and extensions by VIN — including the Honda head gasket and ring extensions and the Ford coolant bulletins.

Checkpoint 3: the swap test — the coil moved to another cylinder, the code cleared, a drive.

Checkpoint 4: the plug — worn, cracked, oily or wet with coolant.

Checkpoint 5: compression, leak-down and a borescope — and on the engines in Route 5, the cooling system pressure test.

Checkpoint 6: the part — only now, with the test that condemned it on the estimate.

Three P0303 traps that cost owners the most

Trap 1: the second coil. A coil that did not fix it the first time will not fix it the second. Lesson: after one swap test that leaves the misfire on cylinder 3, pay for compression and a borescope, not parts.

Trap 2: topping up the coolant. Owners keep adding coolant for months while the misfire comes and goes. Lesson: coolant that disappears with no leak is a diagnosis waiting to happen; ask for the pressure test.

Trap 3: the missing extension. Honda's 2026 head gasket and ring extensions and its injector extension pay for repairs owners are being quoted for. Lesson: ask the dealer to check the VIN for extensions before you approve an estimate, and keep your purchase date and mileage records.

Three P0303 quotes, decoded

These are composite scenarios, not individual customers: each combines details from the documents and complaints above.

Scenario 1: 2017 Ford Escape 1.5 EcoBoost, 90,000 miles, P0303, coolant topped up twice, quote for a coil and plugs. The owner asks for the test in Ford's 22-2322. The cooling system loses pressure, the borescope shows coolant in cylinder 3, and the shop quotes a short block; on Fords and Lincolns, 72 of 115 owner engine figures fall between $7,000 and $10,000, and past 21N12's terms the owner pays. Lesson: on these engines, test for coolant before the coil.

Scenario 2: 2014 Honda Odyssey, P0301, P0302 and P0303, oily plugs, second set of plugs in a year. The owner asks about Honda's piston ring bulletin. With no P0304, the repair is rings on cylinders 1 to 3 — and on a 2014 first sold before September 2016, the 10-year term has run out. Lesson: the plug color and the stored codes decide the repair.

Scenario 3: 2018 Honda Accord 1.5 turbo, P0303, white smoke on cold mornings, quote around $5,000 for a head gasket. A Honda dealer checks the VIN against bulletin 26-003, runs the 18 psi pressure test and borescopes all four cylinders. Coolant at cylinder 3 on an eligible VIN puts the gasket under the 10-year, 150,000-mile term; a new head or block also needs Honda's approval. Lesson: take the quote to a Honda dealer and ask about the extension before paying anyone.

The P0303 plan: 10 minutes, today, this week

10 minutes: read every code and the freeze frame; note whether the light flashes; check the coolant and oil levels cold; swap the cylinder 3 coil if it is easy to reach.

Today: if the light flashes, the car loses power or the coolant is dropping, have it towed. Otherwise run the VIN at nhtsa.gov/recalls, which lists safety recalls only, and ask a dealer by number — the Honda head gasket extension (26-003 on a 2018-2022 Accord CVT, 26-004 on a 2018-2020 manual, the rest in dealer message AEBM08262026901) on a Civic, CR-V or Accord, 26-001 on a 2013-2017 Odyssey, 26-002 on a 2013-2015 Pilot, 20-100 on a 2016-2017 Pilot or 2018 Odyssey, 22-2322 and 21N12 on a 1.5 EcoBoost, 22-2229 on a 2.0 EcoBoost, 24-2257 on a 2021 F-150 PowerBoost, and 01-010/18 on an early 2016-2017 CX-9.

This week: have the swap test, compression, leak-down and, where the coolant is low, the pressure test and a borescope done before any more parts — and get every result written on the repair order.

Sources and documents

Primary documents only. Where a claim in this guide is marked 🟢, it rests on one of the items below, and the reference is given so you can pull the document yourself. Claims marked ⚪ are shop-price estimates carried from PulsCar's repair guides — estimates, not measurements from a dataset we own.

1. Ford 1.5 EcoBoost 19-2375, 19-2139, 20-2100, 21-2269, 22-2134 and 22-2322; Customer Satisfaction Program 21N12; 1.5 GTDI charge air cooler 17-0028; 2.0 EcoBoost SSM 47204, 19-2172, 19-2208, 19-2346, 22-2133 and 22-2229; PowerBoost 22-2017 and 24-2257; 21-2147, 22-2025 and 23-2011; 26-2210; SSM 52419, 52630 and 24-2384; SSM 52455; SSM 53869; 18-2237, 17-2235 and 19-2243; 25-2200, 25-2322 and 25-2572; and the other Ford misfire bulletins in the published list.
2. Honda and Acura 13-078 to 13-082 (among them 13-081 and 13-082 version 12); 25-060, 25-061, 26-001 and 26-002; dealer message AEBM08262026901 and head gasket bulletins 26-003, 26-004, 26-005 to 26-013, 26-016 to 26-019 (among them 26-017), 26-010, 26-097, 26-098 and 26-099; Acura announcement, B26-001, B26-002 and Integra 26-003; 20-100, 21-010 and 18-025; 21-007; 19-032, 19-033, 18-114, 18-137, 18-147 and 19-012; 23-026; the Civic CNG request for parts.
3. Stellantis 09-013-20 REV. A; 09-011-25; 09-017-26 REV. A; 18-161-22; the P0300-series and P030X flash bulletins for Jeep, Ram, Dodge, Chrysler and Fiat, and the MultiAir P106A bulletins, listed in the published file; Chrysler X56 09-002-14 REV. B, read for our P0302 study.
4. Toyota and Lexus T-SB-0010-24 and its revisions; Lexus L-SB-0009-24, L-SB-0008-21 and L-SB-0007-21; the Toyota, Lexus and Scion misfire bulletins and tech tips in the published file.
5. Mazda 01-010/18 and its earlier issues. Land Rover SSM74161. Jaguar SSM74160. Infiniti ITB21-009.
6. Hyundai and Kia 20-01-008H, 20-FL-001H, 18-01-017-1 and 20-FL-006H-1; Kia 165, 186, 181 and 208. GM 23-NA-043, PIP5776, PIP4138 and PIP5628.
7. Audi 2060491/1, 2058309/5 and 2069038/6. Volkswagen 01-21-02. BMW SI B12 10 16. MINI SI M12 11 14. Subaru, Nissan, Mercedes-Benz, Hino and Mack notes are in the published file.
8. PulsCar analysis of NHTSA public data, September 2026: 1,301 complaints naming P0303, a range containing it or a cylinder 3 misfire, each sorted twice, independently; owner-reported amounts; the document list with read status. Data and method.

For the neighboring pages: the P0300 guide, the P0301 guide, the P0304 guide, flashing check engine light and shaking, car running rough, head gasket repair cost and the code index.

Methodology. The complaint set is every complaint in NHTSA's file from 2015 to 21 September 2026 that names P0303 (with spellings using a letter O, a space, a suffix, or the code written without its zero or its P), a code range or list that includes it, or a misfire on cylinder 3 in words — 1,301 in all, 272 of them found by a second, independent search. Every complaint was sorted twice, independently, by written rules fixed before the sorting began (the two sortings matched on the category for 1,185 of 1,301, or 91%, and on stall or power loss for 1,266 of 1,301, or 97%), every disagreement was settled by written rules published with the data, and a final check of the matching sortings against those rules corrected four. Every complaint quoted, and every dollar figure, was read in full. Coverage status is our computation from the printed terms, as of September 2026. Nothing here is a failure rate.

Prices verified July to September 2026 in the repair guides they are carried from, and reviewed quarterly. Technical documents verified September 2026: the 745 documents read in full in our published list — among them Ford 22-2322, 22-2229, 24-2257 and program 21N12, Honda dealer message AEBM08262026901, 26-001 and 26-002, Mazda 01-010/18, Toyota T-SB-0010-24 Rev2, Lexus L-SB-0008-21, Audi 2060491/1 and BMW SI B12 10 16.

Had a cylinder 3 misfire fixed by a pressure test, a bulletin, a software update or an extension — or talked out of a second coil? Email [email protected] with the vehicle, mileage and outcome.