P0306 and P0305 in 2026: Cylinder 6 and Cylinder 5 Misfire — What 280 Documents and 559 Complaints Show

P0306 and P0305 are twins, and a common shortcut treats them as one sentence: "replace the coil and the plug." The documents do not.

P0306 — printed by Toyota as "Cylinder 6 Misfire Detected" and by Mercedes as "Combustion misfiring of cylinder 6 has been detected" — says the engine computer counted too many misfires on cylinder 6. P0305 says the same for cylinder 5. The computer watches the crankshaft speed up with each cylinder's power stroke; when one stroke is weak often enough, it stores a code that names a place, not a part. Cylinder 6 exists only on engines with six or more cylinders, in practice V6, V8 and straight-six engines. Its neighbors are P0300 (random or multiple cylinders, our P0300 guide), P0301 (the P0301 guide, which explains the free coil swap test in depth), P0302, P0303 and P0304, and P0307 and P0308 on V8s. This page is about what makes cylinders 5 and 6 different: on several engines the maker papers single out cylinder 5 or 6 (GM's V6 AFM cylinder 5, the GM and Ram V8 cylinder 6, Chrysler's Pentastar left head).

We went through NHTSA's index of manufacturer communications for papers that name P0305 or P0306, that list a misfire code range containing them, or that discuss a misfire on cylinder 5 or 6, and an independent second search added more. 326 files, 280 distinct documents once exact copies are set aside. We went through 190 representative documents in full and compared the other files with them line by line. Of the 326 files, 259 print P0305 or P0306 somewhere in their own text, most of them as codes of their own, and some only inside a range such as P0300-P0306 or P0301-P0308.

We also went through 601 complaints from NHTSA's file, received from January 2015 through the end of September 2026, that print P0305 or P0306 in any spelling we searched, or that put a misfire on cylinder 5 or 6 in owners' words. Each was sorted twice, independently, by the same written rules; the two sortings matched on the main category in 95% of them (573 of 601), and the rest were settled by written rules; a final consistency check changed 55 rows under the same rules (marked in the published file). 559 describe a misfire on cylinder 5 or 6 on the owner's car; 42 do not. The number that matters most for this page is small: only 70 of the 559 end at a coil, a plug or an injector. The other 489 end mostly inside the engine or nowhere yet; 42 end at software, a cleared code or another cause. Complaints come from owners whose trouble did not end, so none of these shares is a forecast for your car.

By the end you will know which cylinders your maker singles out, which of five routes your P0306 or P0305 is on, what each costs, which extension, bulletin or program applies, and the cheap cause that gets skipped when a coil is quoted first.

Claims marked 🟢 rest on a document listed in the Sources section. 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 601 complaints sorted twice and published.

Words on this page. Engine computer (ECM, PCM): the car's computer. DTC: a trouble code such as P0306. Bulletin (TSB, SSM, PIP): a maker's repair instruction to dealers, not a recall. RSU, RRT: a short-term Ram, Jeep or Chrysler update offer. AFM, DFM, MDS: systems that shut cylinders off to save fuel. Lifter, rocker arm, camshaft: the parts that open the valves. Cylinder leakage test: air is pumped into a cylinder to see where it escapes. Power balance test: a scan-tool test that shows which cylinder contributes less. ODI number: NHTSA's reference number for a complaint. Transverse V6: a V6 mounted sideways, as in most front-drive cars and vans; on many of them the rear bank sits under the intake manifold. Flash: a software update of the computer. Long block: the engine core a shop replaces in an engine job. MIL: the check engine light. Leak-down: another name for a cylinder leakage test; for fuel, how fast the rail loses pressure after shutdown.

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). A misfire code is where that kind of spiral can start — a coil, then plugs, then an injector — so every claim below that rests on a document names it.

What P0306 and P0305 say: a place, not a part

A misfire code is the computer's counting, not a diagnosis. Toyota's papers print each misfire code with its own text — 🟢 "P030500 - Cylinder 5 Misfire Detected." and "P030600 - Cylinder 6 Misfire Detected." — and in the coil papers attach them to a repair only after the dealer has diagnosed a coil fault; the 2018 Camry and 2019 Avalon paper reprograms the computer when the code is stored and the calibration is not yet the latest. Chrysler prints "P0305 - Cylinder 5 Misfire." in a bulletin whose only fix is six new spark plugs, and "P0306 - Cylinder 6 Misfire." in another whose fix is a camshaft kit. Same label, two different parts.

Three things decide what a code means on your car. Which cylinder is 5 or 6. The number is a position in the maker's numbering, and the same number is a different physical place in a transverse V6, a longitudinal V8 and a straight-six. Whether that cylinder is special. On engines that shut cylinders off to save fuel (GM's AFM and DFM, Ram's MDS), certain cylinders carry extra hardware, and the documents name them. Whether the code is real. Ford and Land Rover each print papers saying the computer can name the wrong cylinder, and GM prints one saying the scan tool shows the wrong one.

First: is this really P0306 or P0305? The codes around it

The code can name the wrong cylinder. 🟢 Ford's special service message for some 2024 F-150 PowerBoost trucks says the vehicles "may set incorrect cylinder misfire DTCs while the CSER monitor is active", and tells the technician to "allow the vehicle to run for at least 3 minutes and verify any individual cylinder misfire codes by performing a Power Balance Test." 🟢 Ford's Bronco bulletin does the same for coil-circuit codes (P0352-P0355) and prints "incorrect cylinder to DTC mapping within the PCM"; 🟢 GM's note for 2023 Corvettes with two printed software numbers says the scan tool's Mode 06 page shows cylinder 5 as 7 and cylinder 6 as 8, and to rely on the codes; 🟢 Land Rover's 2017 V8 paper says the mapped codes are wrong except for cylinders 7 and 8. A coil bought for the cylinder in the code is a guess until a power balance test or a swap has agreed with it.

Both codes together. 9 of the 559 relevant complaints print both P0305 and P0306. On a Lexus RX 350 each code can appear in a pair: 🟢 Lexus's L-SB-0008-21 prints "P030200 and P030500 (Cylinders 2 and 5 Misfires Detected)" and "P030300 and P030600 (Cylinders 3 and 6 Misfires Detected)" as companion pairs, and replaces a crank sensor rotor.

Which cylinder is 5, which is 6? The maker atlas

Where cylinder 5 or 6 physically sits comes from the service information for your exact engine.

The do-not-replace lines: what the papers tell a shop not to buy first

A pattern runs through the documents: a large share of the fixes are software, a test or a program, and some papers print a do not before the part. 🟢 GM's PIP6073, a preliminary-information paper for 2025 GM trucks, SUVs and the CT5-V Blackwing, says to swap the ignition coil with an adjacent coil first and prints "Do not replace any other parts such as injectors or ECM unless further diagnosis and SI procedures lead you to a faulty component." 🟢 Ford's SSM 50412 says "Only replace the ignition coil if the misfire concern follows that particular ignition coil." 🟢 Audi's winter-fuel bulletin says "Do not replace any components for this condition since this will not resolve the customer's concern." 🟢 Lexus's two bulletins say "The ECM (PCM) should NOT be replaced as part of the Repair Procedure." 🟢 Chrysler's 6.4L injector paper for Dodge and Jeep says "Do not automatically replace all eight fuel injectors", only those whose Julian date falls in a printed window. 🟢 Ram's July 2026 information-only bulletin for 2025 Hurricane trucks says that if diagnostics find no failed component, "do not replace control modules, emission system components, or other related parts solely as a result of this condition" (a MIL after driving at 6,500 feet or higher and then descending 1,000 feet or more); its printed cause is "PCM Software Under Investigation." A coil is the printed fix in only a few papers, and only after a diagnosis that points at that coil: Toyota's and Lexus's coil-and-flash pair and GM's PIP5038B, PIP5147A and PIP6073.

The other direction has its warnings too. 🟢 GM's PIP5038B for the 2008-2009 3.6L V6 says "The cylinder with the damaged coil may not be the cylinder causing the issue." A coil that looks cooked is sometimes the victim.

The 10-minute check

1. Write down what the car did, and read the full code list (3 minutes). Steady or flashing? Cold start or after warm-up? Did it start with a lurch on acceleration, or at idle? Read the codes with a reader that shows maker codes, and write down every code, not just P0305 or P0306: the pair, P0300 beside it and any P0316 (a misfire in the first moments after start), P0355 or P0356 change the route. Do not clear the codes before the shop sees them unless you are about to test a fix.

2. The coil swap test (only with a steady light and a smooth engine; 5 minutes on a coil you can see). Move the coil from the named cylinder to a neighbor, clear the misfire counters if your reader allows, and drive the same way. If the misfire follows the coil, the coil is the part ($150 to $400 installed in our guides). If it stays on cylinder 5 or 6, the coil is innocent and you have saved the money. On many transverse V6s the rear cylinders sit under the intake manifold; if you cannot see the coil, ask the shop to run the swap and write the result on the invoice. 🟢 Ford's SSM 50412 and GM's PIP6073 print exactly this test. (Our advice: engine off and cool, and check that every plug wire and coil boot clicks home; 🟢 GM's service update 14481 for 2014 inventory trucks and Corvettes (a P0300 paper, expired October 2015) found that a misfire code can come from "Loose spark plug wires" and fixed it by "Pull and reseat wires at both ends.")

3. Look at the coolant and the oil (1 minute). A coolant reservoir that drops with no leak on the ground, white smoke on a cold start, a sweet smell, a milky oil cap: any of these with a cylinder 5 or 6 misfire is the cylinder-sealing family, and the checks are a pressure test and a cylinder leakage test, not a coil. In the complaint file 86 owners ended at coolant in the cylinder, a head gasket or a cracked head, 52 of them on a Chrysler Pacifica.

4. Listen at idle (1 minute). A tick that does not go away after warm-up, with a misfire on 5 or 6 on a GM, Ram, Ford V8 or Pentastar engine is the valvetrain family until proven otherwise: 🟢 GM's 15-06-01-002O (a P0300 paper) says to "Thoroughly inspect the camshaft and lifters for any damage to the lobes or rollers."

5. Find your VIN and paperwork (2 minutes). Programs and updates are tied to VINs, build dates and in-service dates. Ask a dealer whether a bulletin, a software update, a recall or an extension exists for your engine, and ask for the number. Bulletins are dealer repair instructions, free only inside a warranty or a program.

Six P0306 and P0305 situations, and which is yours

"A steady light, the car runs smoothly, and the shop wants a coil and plugs." The free swap test comes first. → Route 1.

"The code appeared only on cold starts or at warm-up, on a late-model Jeep, Ram, Dodge or Ford." Several makers print a software cause for exactly this. → Route 2.

"A 2016-2019 Honda Pilot, 2017-2019 Ridgeline or 2018-2019 Odyssey with P0300 through P0306." Honda prints a program that replaces fuel injectors, 10 years or 150,000 miles. → Route 2 for the paper and Route 3 for the part.

"A 2011-2013 Chrysler 3.6L van, Jeep, Dodge or 300 with P0306, or a 2017-2018 Pacifica with P0305 or P0306 and a dropping coolant level." Chrysler's X56 paper replaces the left cylinder head after a leakage test; for the 2017-2018 Pacifica the complaint file is dense, and the one maker paper in our set that lists a 2018 Pacifica with these codes (none lists the 2017) is an information-only paper about worn intake camshaft lobes and rocker arms. → Route 4.

"A GM V8, a Ram 5.7L or a Ford V8 with a tick that does not go away and a misfire on 5 or 6." Lifters, rocker arms and camshafts, and the papers name them. → Route 5.

"The light flashed, the engine shook and then it stalled." Do not drive it. Have it towed, ask for the full code list, and ask the shop for the swap test and a leakage or compression test before it quotes a coil or engine work. → Routes 1, 4 and 5.

The P0306 and P0305 price ladder, from the bottom up

Our guide figures are typical independent-shop prices; owners' figures are mostly quotes, and the high ones are mostly cases where a dealer wanted an engine. Read the ladder as the reason to work cheap-first. The expensive mistake is not the coil; it is paying for a coil, then plugs, then an injector on a guess while the cause was a cylinder that was not sealing, and then driving it until the engine fails.

The five P0306 and P0305 routes, cheapest first

A misfire code says one cylinder's power stroke was weak. Each route below is a reason it can be weak, ordered by what it costs to rule out. Owner counts come from the 559 relevant complaints; "came back" means the owner says the same light, code or symptom returned or the repair did not hold. Complaints come from owners whose trouble did not end, so none of these shares is a forecast for your car.

Route 1 · Spark on the cylinder: plug, coil, boot and wire — $0 yourself, $200 to $780 at a shop

What it is. The spark on cylinder 5 or 6 is weak or absent: a worn or cracked plug, a plug with the wrong gap, a coil with a heat-damaged tower, a loose wire or boot, a bad ground.

What the documents say. 🟢 Chrysler's bulletin for some 2020-2021 3.6L Pentastar vehicles built in autumn 2020 prints "3.6L Pentastar Upgrade Spark Plug Internal Crack" and the note "all six spark plugs must be replaced for this Repair Procedure if one DTC is found"; the paper's RRT "will expire 18 months after the date of issue", December 2020 plus 18 months, so it has ended. 🟢 Ford's paper for the 2011-2013 F-150 3.5L EcoBoost says "Inspect the spark plug for signs of carbon tracking" and replaces "all six spark plugs and spark plug coil boots." 🟢 For the 2023 Challenger 6.2L the cause is "Incorrect spark plug gap", 0.60 mm nominal, and the paper says it "does not involve the replacement of all sixteen spark plugs, or any ignition coils" (two plugs per cylinder on that engine) 🟢 GM's PIP6073 for 2025 trucks says "This condition may be caused by a faulty ignition coil assembly." 🟢 Toyota and Lexus print a coil replacement for P0301-P0306 on some 2016-2019 hybrids, but only where the answer to "Does the diagnosis indicate a malfunctioning ignition coil?" is yes, together with a computer flash, under a 96-month, 80,000-mile emission warranty.

What the owners report. 31 complaints end at a coil and 14 at a plug (45 together, 8% of 559), and 29 of those 45 say it came back. A 2007 Ford Edge owner wrote that the car "WAS FOUND TO HAVE A MELTED #5 COIL" and, after a new coil, "#5 MELTED AGAIN, PCM PROBLEMS." A 2003 F-150 owner's plug left the engine: "FOUND THE SPARK PLUG HAD EJECTED FROM CYLINDER NUMBER 6", with a loss of power in traffic on a hill.

The cheap cause that gets skipped. A connector or ground that was never checked. GM's paper for 2014 trucks found the misfire code came from "Loose spark plug wires" and the cure was "Pull and reseat wires at both ends" with no parts; Maserati's is a torque check on the coil grounds (10 Nm). A coil quote that skips the swap test and the plug inspection skips the cheapest tests there are.

Fix it yourself. The swap test above and a look at the plug and boot, engine cold and off. (Our advice: do not pull a coil from an engine with the check engine light flashing and the engine running, and do not force a plug that sits in an aluminum head; ⚪ plugs are $200 to $450 installed on a transverse V6 in our guides because of access.)

At the shop — say this: "Before I buy a coil: did the misfire follow the coil when you swapped it, and was the plug on that cylinder looked at? Please write the swap result on the invoice."

Route 2 · Software, programs and what the maker already knows — often free inside a program

What it is. The computer's misfire logic, fuel calibration or cold-start strategy sets the code on an engine that is mechanically fine, or a maker has a program that covers the real fault. This is the route where the papers are most generous and most easily missed.

What the documents say. 🟢 Toyota's T-SB-0071-18 reprograms the engine computer on 2018 Camrys and 2019 Avalons with the 2GR-FKS V6 for "P030500 - Cylinder 5 Misfire Detected." and "P030600 - Cylinder 6 Misfire Detected." at "High engine speed (5000 - 6500 rpm). High engine load (100%+)." 🟢 Chrysler's 2026 bulletins for the 3.6L in Wranglers, Gladiators, Grand Cherokees and Durangos print "P0305-00 - Cylinder 5 Misfire (Active or Stored status set during cold start catalyst heating)" with the cause "PCM software", and the Hurricane 3.0L trucks get the same treatment. 🟢 Ram's TSB 18-002-25 for the 2023 5.7L Hemi prints "P0306 - Cylinder 6 Misfire." and "P3441 - Cylinder 6 Deactivation Control Circuit" with "CAUSE: PCM Software." 🟢 Ford's 24-2191 for the 3.5L PowerBoost F-150 says "This may be due to the software level of the PCM." 🟢 Audi's RS 6 and RS 7 bulletin says "The ECM software has been optimized."

Programs: 🟢 Honda's 20-100 and 21-010 extend the warranty on the fuel injector repair for P0300 through P0306 (20-100 also covers a software update) to "10 years from the original date of purchase or 150,000 miles, whichever comes first" on some 2016-2019 Pilots, 2017-2019 Ridgelines and 2018-2019 Odysseys, by VIN (Route 3 has the injector part). 🟢 Lexus's L-SB-0008-21 replaces a crank sensor rotor and reflashes the computer on 2018-2021 RX 350 for companion pairs, covered by "72 months or 70,000 miles" from the in-service date. Two cautions from the same pile: 🟢 the Challenger 6.2L re-gap paper (09-016-24) was followed by a separate computer-flash paper (18-035-26), which was later converted to "information only" because "The software previously used to support this TSB is no longer available"; and 🟢 Ram's July 2026 bulletin for 2025 Hurricane trucks has no fix at all, only "PCM Software Under Investigation."

What the owners report. 3 complaints end at a program or software only, and 13 at a shop that found nothing or cleared the code (9 of those 13 say it came back). 105 of the 559 mention a recall, a bulletin, a program or a dealer calling it a known issue (19%). A 2019 Odyssey owner was towed with "PO300 PO3054 and PO306 misfires" (as written); the dealer said bad gas, and the owner writes they had no idea of "an active warranty recall on the fuel injectors" and spent 16 months going back and forth. A 2018 Grand Cherokee complaint says the dealer found a cylinder 5 failure and the vehicle was repaired, "however, the sensor software update failed to perform as needed."

The cheap cause that gets skipped. The program itself. Honda's extension covers original and later owners, and owners who paid for these repairs earlier may be eligible for reimbursement; one Odyssey owner writes that nobody mentioned it for 16 months.

Fix it yourself. Nothing to repair; the work is a phone call. (Our advice: ask the dealer to run your VIN for open programs, software updates and extensions by name; ask for the bulletin number, not "a software update.")

At the shop — say this: "Is there a bulletin, an extension or a software update for my engine and these codes? Please give me the number, and tell me whether it is still open for my VIN."

Route 3 · Fuel and wiring: injectors, harnesses, grounds and the fuel supply — ⚪ $150 to $700 an injector installed

What it is. The cylinder gets too much or too little fuel, or the signal to its coil or injector is broken somewhere between the computer and the part.

What the documents say. 🟢 Honda's 20-100 says "debris from the high pressure pump or the fuel injector machining process can cause internal wear or clogging inside one or more injectors" and, for P0300 through P0306 (or P219A or P219B) alone, "Replace the fuel injectors", 2.2 to 2.6 hours depending on the model. 🟢 Ford's 20-2324 for the 2018 F-150 2.7L has the technician watch the fuel rail pressure fall; "below 6.9 kPa (10 psi) within 30 seconds" (the paper prints both numbers; 10 psi is about 69 kPa, so ask which one the procedure uses) means the direct injectors are replaced (4.9 to 5.0 hours), on trucks built before 12 July 2018. 🟢 Chrysler's 14-003-22 for 2021 6.4L Challenger, Charger, Durango, Grand Cherokee and Wrangler engines says "Do not automatically replace all eight fuel injectors"; only those with printed Julian dates, a rapid service update that ended in 2023. 🟢 Ford's 25-2569 for the 2021-2025 F-150 PowerBoost says the codes P0301-P0306 and P0201-P0206 "may be due to the engine harness contacting the hose crimp end or spring clamp tangs", fixed by shielding the harness and, where the clamp tangs point at it, rotating the hose clamp 180 degrees. 🟢 A Chrysler STAR case record for a low-mileage vehicle with P0306 (the page shows a 3.6L Dodge Challenger) notes: verify the computer software, then "inspect K18 circuit for any terminal damage" and repair it with a kit.

What the owners report. 25 complaints end at an injector (11 say it came back); 26 end at another cause: a wiring harness, a connector, the oil cooler, timing chain, fuel quality or the computer (8 came back). A 2021 Sierra owner: "Once the injector failed, the vehicle would violently shake when trying to accelerate." A 2018 Atlas owner traced a cylinder 6 injector to "massive carbon build up." A 2017 Pacifica owner says a warped plastic oil cooler "cause failure of bay 3 and 5 fuel injectors which caused multiple cylinder misfire." Owners' injector figures are few: two quotes, $2,000 and $4,000.

The cheap cause that gets skipped. A harness against a hose clamp, a terminal pushed out of a connector, a ground. Ford prints 0.9 hour for the hose-clamp job, plus 0.7 hour if wires need repair; the part is small.

Fix it yourself. Only the looking: a harness rubbed bright against a clamp, a connector that is not seated. (Our advice: do not splice injector or coil wiring in a driveway; a bad splice creates the next code.)

At the shop — say this: "Was the fuel pressure leak-down checked, and was the harness to cylinder 5 or 6 wiggle-tested with the engine running? Please give me the measurement, not 'the injector is bad.'"

Route 4 · The cylinder is not sealing: coolant, a head gasket or a cylinder head — $1,200 to $13,000

What it is. Coolant or oil gets into cylinder 5 or 6, or the valves and seats do not seal, so the cylinder cannot burn its charge. A new coil does nothing for it.

What the documents say. 🟢 Chrysler's X56 bulletin, for 2011-2013 3.6L Journeys, 200s, Avengers, Challengers, Chargers, 300s, Grand Caravans, Town and Country vans, Durangos and Grand Cherokees, and 2012-2013 Wranglers, with "P0300, P0302, P0304 or P0306", says "Perform a cylinder leakage test on cylinders 2, 4 and 6", "Do any of the cylinders exhibit leakage of 25% or greater?", and then "Replace the left cylinder head" for 8.2 to 10.2 hours; the extended warranty is in other Chrysler papers, not in this one. 🟢 Ford's 19-2384 for the 2016-2017 F-150 2.7L built April 2016 to January 2017 says rough idle with oil consumption of more than a quart in less than 3,000 miles "may be due to a concern with the cylinder head valve guides" and "Replace both left and right cylinder heads"; its twin SSM 54504 covers Edge, MKX, Continental, Fusion and MKZ with the 2.7L or 3.0L.

We found no maker paper in our set about coolant in the cylinder or a head gasket for the complaint file's biggest group, the 2017-2018 Chrysler Pacifica; the only paper that lists a 2018 Pacifica with these codes is the 2025 bulletin on camshaft and rocker wear, and none lists the 2017. That is a finding about our set, not proof that no such paper exists.

What the owners report. 86 complaints end at coolant in the cylinder, a head gasket or a cracked head, and 25 say it came back. 52 of the 86 are Chrysler Pacificas; of the 69 Pacifica complaints in the set, 62 are model year 2017 or 2018. A 2018 owner wrote: "Leaking coolant in cylinder 5 leading to a misfire and check engine light. Dealer reports this is a known issue and only replacing the engine will fix", and says Chrysler is not doing anything about it. A 2017 owner's dealer found "coolant on cylinder 5", and the owner was quoted $13,000. A 2004 4Runner owner's dealer found a head gasket leaking antifreeze into cylinder 6, "CAUSING P0306", and replaced both head gaskets for $2,644.91. A 2021 Lincoln Nautilus owner reports the same on cylinder 6.

The cheap cause that gets skipped. The cooling system's own pressure test and a cylinder leakage test. ⚪ A compression or leak-down test costs $100 to $300; the head gasket quote that follows is $1,500 to $5,000 in our guides, and owners' figures run from $1,200 to $13,000.

Fix it yourself. The looking: the coolant level over a week, the oil cap, the exhaust smoke on a cold start, a cold-engine pressure test kit if you own one. (Our advice: if coolant is dropping, stop driving; a cylinder that fills with coolant can damage an engine quickly.)

At the shop — say this: "Please run a cylinder leakage test or a pressure test before you quote parts, and tell me the percentage on cylinders 5 and 6. Is there an extension for my engine and VIN?"

Route 5 · Valvetrain and cylinder deactivation: lifters, rocker arms, camshafts and engines — $2,000 to $44,000

What it is. The parts that open the valves wear or fail on one cylinder: a collapsed lifter, a worn camshaft lobe, a bent pushrod, a rocker that does not latch. The cylinder misfires, the engine ticks, and the damage spreads.

What the documents say. 🟢 GM's 15-06-01-002O (a P0300 paper) for 2014-2023 5.3L and 6.2L trucks, SUVs and some cars says to inspect the camshaft and lifters for damage and, if worn, replace them: "It is not necessary to replace the engine assembly." 🟢 GM's 23-NA-043 for 2020-2021 trucks and SUVs with the 5.3L or 6.2L built from September 1, 2020 to March 31, 2021 says "This condition may be caused by an Internal lifter concern." and, over 16,000 miles, to replace the lifters and guides on the affected bank only: "Do Not replace both banks." 🟢 GM's 21-NA-036 for the 3.6L and 3.0L V6 names cylinders 2 and 5 and two causes: oil leaking past the AFM solenoid, or "the rockers on one of these cylinders not latching". 🟢 Chrysler's 2025 bulletin for the 3.6L says the codes may be related to "worn intake camshaft high lift lobe(s), and/or intake rocker arm(s) high lift slider wear", "Typical" failure at 10,000 to 60,000 miles, with kits 68661147AB and 68661146AA instead of the long block. 🟢 Ford's 25-2572 for 7.3L and 6.8L V8s with an upper-engine tick says "This may be due to camshaft and/or valve tappet having excess wear", starts with a power balance test and a plug, wire and coil swap, then an oil-filter look for metal, and ends at a camshaft and tappet kit or a long block, roughly 10 to 23 labor hours depending on the truck.

What the owners report. 143 complaints end at a lifter, rocker, camshaft or valve (the largest group, 26%), 81 at an engine failure or replacement, and 45 of the 143 say it came back. A 2012 Durango owner: "BAD CAMS IN LESS THAN 100,000 MILES. ENGINE MISFIRE ON 5TH CYLINDER, UNABLE TO ACCELERATE QUICKLY, CHECK ENGINE LIGHT FLASHING. $4,700 REPAIR." A 2011 Charger owner's car went into "LIMP" mode at 70 mph from a bad lifter on cylinder 5, over $4,000. The median mileage where a complaint ends at this route is 100,000.

The cheap cause that gets skipped. The compression test. Only a fraction of complaints mention one, and where it is mentioned it reads differently: a number, not an opinion. ⚪ $100 to $300, and it says whether to spend on a coil or stop.

Fix it yourself. Only the listening and the oil: a tick that grows after warm-up, metal in the filter. (Our advice: a misfire on cylinder 5 or 6 with a tick on a GM, Ram, Ford V8 or Pentastar is not a driveway job, and driving it on can turn a lifter into a camshaft and then an engine.)

At the shop — say this: "What was the compression or leakage on cylinders 5 and 6, and did you look at the camshaft and lifters? Is my engine in a bulletin or program for this tick?"

The coverage file: which papers and programs run in September 2026

Most papers above are dealer repair instructions, not coverage. The status column is our computation from the printed terms, as of September 2026, and a start date the paper does not print is a start date we cannot compute.

The recalls are for causes, not codes. We found no NHTSA recall (recalls since 2010) that names P0305 or P0306. The nearest is the Isuzu recall above. A recall in your VIN shows at nhtsa.gov/recalls; an emissions program may not, so ask the dealer.

What 559 complaints about a cylinder 5 or 6 misfire show

How we went through them. We went through every complaint in NHTSA's file received from January 2015 through the end of September 2026 that prints P0305 or P0306 in any spelling we searched, or puts a misfire on cylinder 5 or 6 in owners' words: 426 from our first search, and 175 more from an independent second search for what the first one missed (170 of them relevant). Each was sorted twice, independently, by the same written rules, and the two sortings matched on the main category in 95% of cases (573 of 601). The rest were settled by written rules, published with the file.

How to read the table. A complaint "ends at" the repair that finally fixed it or, if nothing did, the cause a shop named last; "came back" means the owner says the same light, code or symptom returned after a repair or a reset, or that the repair did not fix it.

Is it the coil? Of the 559, 70 end at a coil, a plug or an injector (13%); 310 end inside the engine: valvetrain, coolant or an engine failure (55%). Of the 45 that end at a coil or plug, 29 say it came back, against 45 of 143 for valvetrain and 25 of 86 for coolant. Read that with its caveat: an owner whose plug or coil job fixed the car rarely writes to a federal agency, so the file overstates the engine and understates the coil.

Which cylinder. 221 name cylinder 5 only, 178 cylinder 6 only, and 160 name 5 or 6 together with other cylinders. Cylinder 5 is more often a valvetrain case (32% against 26% for cylinder 6) and a coolant case (19% against 14%); a coil, plug or injector ends only 8% of the cylinder 5 complaints and 12% of the cylinder 6 ones. Where several cylinders misfire, 19% end at an ignition or fuel part, the highest share of the three groups.

Which cars. Chrysler is 98 of the 559 (Pacifica 69), then Chevrolet 72, Ford 63, Dodge 63, GMC 55, Jeep 42, Honda 32, Ram 24, Toyota 18 and Kia 18; complaints, not failure rates. The pattern by maker is sharper than the pattern by code: 52 of the 69 Pacifica complaints end at coolant or a head gasket; 41 of Chevrolet's 72, 26 of GMC's 55 and 28 of Dodge's 63 end at a lifter or camshaft.

What happened. 194 describe a stall, a loss of power or a limp mode (35%), 50 a flashing check engine light, and 141 an engine replacement, rebuild or major repair done, quoted or required (25%). 105 mention a recall, a program, a bulletin or a dealer calling it a known issue (19%). 41 use the words crash, accident or collision, most of them as a risk or a near miss; 45 mention an inspection or an emissions test.

Is a cylinder 5 or 6 misfire a coil problem, and when does it mean the engine? PulsCar sorted, twice and independently, the 601 complaints in NHTSA's file from 2015 to the end of September 2026 that print P0305 or P0306 or describe a misfire on cylinder 5 or 6: 559 describe the fault on the owner's car, 194 of them a stall, a loss of power or a limp mode, and 50 a flashing check engine light. Only 70 of the 559 end at a coil, a plug or an injector; 310 end at a lifter, a camshaft, coolant in the cylinder or an engine failure. Counts are complaints, not cars, and owners whose coil fixed it rarely write to NHTSA, so read them as a map of where trouble goes and not as a failure rate for your car.

The 140 complaints that print the code

140 of the 559 print P0305 or P0306 as a code (77 P0305, 72 P0306, 9 both), and they are not the group you would expect from the parts-store advice: 8 end at a coil, a plug or an injector, 43 at no cause found yet, 25 at a valvetrain part, 25 at coolant or a head gasket, 23 at an engine failure, 10 at a shop that found nothing and 6 at software or another cause. 52 describe a stall or loss of power and 41 say the problem came back. The part is usually not the first one quoted.

What owners say they paid

Of the 559 relevant complaints, 86 state a dollar figure tied to the repair, 106 figures in all: 62 quotes, 31 bills, 10 amounts paid, 2 amounts offered and one where the narrative does not say. The figures are what owners wrote, not audited invoices, and we publish them with ODI numbers. The rows are in the ladder above: a coil or plug job $200 to $780, a head or head gasket $1,200 to $13,000, valvetrain $2,000 to $25,000, engine work (replacement, rebuild, teardown or timing chain) $3,800 to $44,000.

How much does it cost to fix P0306 or P0305 in 2026, and when does a coil quote mean the wrong repair? PulsCar took every dollar figure in the 559 relevant complaints that meets one written inclusion rule: 106 figures in 86 complaints, 62 of them quotes. Coil or plug work runs $200 to $780 (median $370, six figures), injector quotes $2,000 and $4,000, head and head gasket work $1,200 to $13,000 (median $5,000), lifters, camshaft or valves $2,000 to $25,000 (median $4,290) and engine work (replacement, rebuild, teardown or timing chain) $3,800 to $44,000 (median $10,000). The top figure, $44,000, is what BMW quoted a 2019 M5 owner for an engine failure, with $4,000 offered toward it. Read the rows as the shape of the problem and not as a price list for your car.

Why P0306 and P0305 come back after a repair

The cause was never the spark. A coil on cylinder 6 fixes a coil; it does not fix a cylinder that fills with coolant or a lifter that has collapsed, and in the complaint file that is where most trouble ends. The repair fixed the wrong cylinder. Ford and Land Rover print papers saying the code can name the wrong cylinder; confirm with a swap or a power balance test. A lifter was replaced, not the camshaft. GM's 15-06-01-002O tells the shop to inspect the camshaft and lifters and replace both if damaged, and 23-NA-043 replaces all lifters and guides together (on the affected bank only above 16,000 miles); one 2014 Silverado owner says the same lifter was replaced twice in a couple of weeks. A head gasket was replaced and the head was warped. Chrysler's X56 paper replaces the whole left head when a leakage test fails, not just the gasket. The software was never offered. Many papers for Toyota, Lexus, Ram, Audi and Ford are flashes, and a shop that does not look them up sells parts.

Can you drive with P0306 or P0305?

It depends on how the car behaves, and this is our rule, not any maker's: none of the documents we checked (280 distinct, 190 read in full) says to stop driving. A steady light with a smooth engine, no ticking, no coolant loss and no smoke: a shop within days, and not on the highway. A flashing light, shaking, a loss of power, a tick that grows, white smoke, a sweet smell or a dropping coolant level: do not drive it to the shop; have it towed.

Is it safe to drive on a cylinder 6 or cylinder 5 misfire code? PulsCar's reading of 559 federal complaints is that the code alone does not say, and the behavior of the car does. 194 of the 559 describe a stall, a loss of power or a limp mode, 50 a flashing check engine light, and 41 use the words crash, accident or collision. A 2014 GM service update on loose spark plug wires (inventory vehicles, expired October 2015) warns that continued operation with that misfire "could result in damage to the catalytic converter." A tow costs far less than a converter, which is $700 to $4,500 in our guides, and an engine costs more. The papers set no rule of their own; ours is that a flashing light is the end of the trip.

Should you buy a used car with a P0306 or P0305 in its history?

Ask what was found, not what was replaced. A history with a plug, a coil, a software update or a program repair and a clean drive afterwards is better than the same code coming back; in the complaint file, where owners wrote because trouble continued, 29 of the 45 whose complaint ends at a coil or a plug say it came back. Ask for the invoice that names the cylinder and the test that found the fault. On a 2011-2013 Chrysler 3.6L ask whether the left head was done under the X56 program; on a 2017-2018 Pacifica, a GM or Ram V8 or a Ford 7.3L, ask for the oil-change history, the coolant history and a cold-start listen; and have a shop run a cylinder leakage or compression test on cylinders 5 and 6 before you sign. A pre-purchase check is $100 to $300 (⚪); engine work ran $3,800 to $44,000 in the owner reports (the top figure is a BMW M5 quote).

Clearing P0306 or P0305 before an inspection

A cleared code returns if the cause is a collapsing lifter, a leaking head gasket or a half-seated wire, and an emissions test needs the car's self-checks to have run again. Fix first, drive several normal trips, then test. (Our advice: a car whose codes were cleared recently can be turned away as "not ready" at an emissions test.)

What the papers tell a shop to do with P0306 or P0305, checkpoint by checkpoint

Checkpoint 1 — verify the cylinder. Ford: power balance test, and on the 2024 F-150 PowerBoost wait three minutes after a cold start; GM: rely on the stored codes, not the scan tool's Mode 06 page. Checkpoint 2 — the swap. Ford and GM: move the coil and the plug and see whether the misfire follows. Checkpoint 3 — the software. Toyota, Chrysler, Ram, Ford, Mercedes and Audi: the calibration level first. Checkpoint 4 — the pressure. Chrysler: cylinder leakage test, 25% or greater means the left head; Honda: for P0300 through P0306 alone, the injectors (the cylinder test is for P0420 and P0430); Ford (2018 F-150 2.7L): fuel rail pressure falling below 6.9 kPa (10 psi, as printed) within 30 seconds of shutdown. Checkpoint 5 — the engine. GM and Ford: camshaft and lifters inspected, the oil filter checked for metal, and the engine replaced only if the damage says so.

Three P0306 and P0305 traps

Trap 1 · Buying the coil from the code. The code names a cylinder, not a coil. In the file 31 complaints end at a coil, 143 at a lifter or camshaft and 86 at coolant or a head. Ford's SSM 50412 says to replace the coil only if the misfire follows it, and GM's PIP6073 says to swap it with an adjacent coil and re-test first.

Trap 2 · Driving on a ticking engine. A misfire on 5 or 6 with a tick on a GM, Ram, Ford or Chrysler V6 or V8 is a lifter or a cam until a compression or leakage number says otherwise; drive it and a lifter can become a camshaft.

Trap 3 · Taking an expired program for a closed door. Several programs here ended on a printed date, and others never had one; Honda's runs ten years from purchase, Chrysler's X56 has terms in a paper this file does not print, and Isuzu's recall has no end date. Ask the dealer by number; "that's out of warranty" is not an answer.

Three P0306 and P0305 claims, decoded

"P0306 means the coil on cylinder 6 is bad." It means cylinder 6 misfired; in the papers the causes include a plug, a coil, a ground, an injector, software, a head, a lifter and a camshaft.

"It is just a misfire, drive on." None of the papers says stop, and none says to keep driving; 🟢 a 2014 GM paper on loose plug wires warns of converter damage, and in the file 194 of the 559 describe a stall, a loss of power or a limp mode.

"There is a recall." For some causes and cars, yes, such as the Isuzu coil-pack fuse recall; for the code in general, no recall names P0305 or P0306.

The P0306 and P0305 plan: 10 minutes, today, this week

Today (10 minutes, steady light and smooth engine only). Engine off, check that every plug wire and coil boot clicks home; read every code and write down the mileage; do the coil swap test; look at the coolant level and the oil cap. Today (VIN). Ask a dealer about open programs, software and extensions for your engine, by name. This week. If the misfire stays on the cylinder, ask for a power balance test and then a leakage or compression test before a part is ordered. Before you pay. Ask which measurement showed the part.

These are composite scenarios, not individual customers; the dollar figures are owner reports from the file. If you drive a 2018 Pacifica with a cylinder 5 misfire and a coolant level that is dropping, ask for a pressure test and a leakage test before a coil quote; one 2017 owner was quoted $13,000 and a 2018 owner's dealer said only an engine would fix it. If you drive a 2019 Silverado or a Ram 1500 with a cylinder 6 misfire and a tick, ask for a compression number and for GM's or Ram's valvetrain papers by number; Silverado and Ram 1500 owners report $4,500 to $10,100 for lifters and cams (a 2015 Sierra owner was billed $2,853). If you drive a 2018 Camry with P0305 and P0306 at full throttle, ask for Toyota's T-SB-0071-18 before a coil: it is a computer flash for the 2018 Camry V6, covered under the emission warranty for 96 months or 80,000 miles from the in-service date; most 2018 Camrys have passed 96 months by now, so ask whether yours is still inside it.

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. Toyota and Lexus: T-SB-0071-18 Rev2; T-SB-0148-19; L-SB-0044-19 Rev1; L-SB-0008-21 Rev1.
2. Honda: 20-100 Version 2 and its warranty extension letter; 21-010.
3. Stellantis (Chrysler, Dodge, Jeep, Ram): 09-002-14 Rev. B (X56); 09-013-20 Rev. A; 09-010-21; 14-003-22 Rev. A; 18-002-25; 09-011-25; GPOP 9100143; 09-016-24 and 18-035-26 Rev. A; 18-003-26 Rev. A; 18-072-26; STAR case S2008000135.
4. General Motors: PIP6073; PIP5038B; PIP5147A; PIP4568S; 21-NA-036 Version 2; 15-06-01-002O; 23-NA-043; service update 14481; 23-NA-200.
5. Ford: SSM 50412; SSM 52318; 18-2047; 19-2384; SSM 54504; 20-2324; 24-2191; 25-2569; 25-2572; 26-2011; 24-2406; TSB 14-0160.
6. Mercedes-Benz, Audi, Infiniti, Maserati and Land Rover: Mercedes LI07.70-P-066276 Version 9; Audi 2071263/5 and 2058038/5; Infiniti EC21-012; Maserati DS 25-25; Land Rover Q057 and N049NAS1.
7. Recall: Isuzu, NHTSA campaign 23V-564 (Isuzu V2305), coil-pack fuse holders.
8. PulsCar analysis of NHTSA public data, October 2026: 601 complaints about a misfire on cylinder 5 or 6, each sorted twice by the same written rules; owner-reported amounts; the document list with check status and links. Complaints, amounts, documents, the sorting rules and how we did it (CC BY 4.0).

For the neighboring pages: the P0300 guide for random misfires, P0301, P0302, P0303 and P0304 for the other cylinders, spark plug replacement cost and spark plugs replacement cost, fuel injector replacement cost, head gasket repair cost, a flashing check engine light with a shaking car, a car running rough, a car shaking when idle, what a check engine light means and how much a diagnostic costs.

Methodology. The complaint set is every complaint in NHTSA's file received from January 2015 to the end of September 2026 that prints P0305 or P0306 in any spelling we searched, or puts a misfire on cylinder 5 or 6 in owners' words (first search, 426), plus 175 more from an independent second search: 601 in all. Every complaint was sorted twice, independently, by the same written rules; the two sortings matched on the category in 95% of them (573 of 601), the rest were settled by written rules, and a final consistency check changed 55 rows under the same rules (marked in the published file). 559 describe the fault on the owner's car. Dollar figures were included under one written rule. The document set is NHTSA's index of manufacturer communications (326 files, 280 distinct documents, 190 read in full, the rest compared line by line); model years, engines and coverage terms are as printed, never taken from NHTSA's index. Counts are complaints, not cars, and nothing here is a failure rate. The files are published: complaints, amounts, documents, the sorting rules and how we did it (CC BY 4.0).

Prices verified July to October 2026 in the repair guides they are carried from and in the owner reports above, and reviewed quarterly. Technical documents verified October 2026: the 326 files (280 distinct documents) in our published file, of which 190 files were read in full, 3 read from page images and the rest compared line by line with a copy that was.

Had P0306 or P0305 cleared by a plug, a coil, software, a program, a head or a lifter? Email [email protected] with the vehicle, mileage and outcome.