P0302 on Honda: How to Diagnose & Fix
Cylinder 2 Misfire Detected
8 Honda models · 16 documented issues · 6 critical · $20-$8,000 repair
P0302 on Honda by model: symptoms, diagnosis and fix
The 1.5L turbocharged Earth Dreams direct-injection engine (L15B7) accumulates heavy carbon deposits on intake valves and ports because fuel is injected directly into the cylinder, bypassing the intake valves. Unlike port-injection engines, no fuel washes the intake valves clean. Owners report symptoms beginning at 40,000-60,000 miles. Carbon buildup restricts airflow, causing rough idle, misfires, reduced power, and reduced fuel economy. This is inherent to direct-injection technology and affects all 10th-gen Civic 1.5T variants.
Common Symptoms
- Rough idle or stumbling at idle
- Misfires on cold start (P0300-P0304)
- Hesitation or stumbling during acceleration
- Reduced power output compared to new
- Decreased fuel economy (2-4 mpg reduction)
- Hard cold starts
- Occasional rough running that improves when warm
How to Fix
Walnut blasting (walnut shell media blast cleaning) of intake valves every 40,000-60,000 miles is the industry-standard solution: $300-500 at independent shops, $500-800 at dealers. Chemical intake cleaners (CRC GDI IVD Intake Valve Cleaner #05319, Liqui-Moly Valve Clean) used every 10,000 miles can slow buildup but do not fully remove existing deposits. Top-tier gasoline (Shell V-Power, Chevron Techron) contains detergent additives that help prevent buildup. Catch-can installation ($80-150) reduces oil vapor contributing to buildup.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- CRC GDI IVD Intake Valve & Turbo Cleaner 05319, 11 ozOEMCRC 05319
Manufacturer-directed chemical cleaning option for diagnosed or suspected light-to-moderate GDI intake deposits Fitment/availability: 2016-2021 Civic 1.5T only after ruling out bulletin/software, injector, ignition, boost and mechanical …
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Owner tips & cautions
- TipCivicX.com consensus: Schedule walnut blast cleaning at 50,000 miles regardless of symptoms - visible buildup starts at 40k miles and only gets worse. Independent shops charge $300-400 vs dealer $600+
Sources for this issue (3)
Honda bulletin 19-038 documents specified misfire/rich-mixture codes (P0300-P0304, P0172) or engine whirling noise on 2016–2018 Civics with the 1.5L engine. Applicability and coverage require a VIN check.
Common Symptoms
- Misfire or rich-mixture fault codes
- Whirling noise from the engine
How to Fix
Ask Honda to check VIN eligibility and prior repair history. Complete 18-137 first only if it applies to this VIN and has not already been completed. Bulletin 19-038 then separates a fouled-spark-plug branch from camshaft/rocker diagnosis. Follow the applicable technician procedure; if the specified conditions are not found or symptoms remain, continue normal troubleshooting. Do not assume free coverage today.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- NGK 95112 / ILZKAR8H8S spark plug — non-Si repair branch onlyFits 2016-2018 · EX-T / EX-L / Touring / SportOEM12290-59B-003Cross-refNGK 95112, ILZKAR8H8S
Confirm VIN and current service parts before purchase.
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Sources for this issue (1)
Two independently filed NHTSA complaints on near-new 2025 Civics describe the same failure: sudden rough idle and near-stall shortly after startup at roughly 2,000 and 9,000 miles. In the first, the dealer found active misfires on all four cylinders with all four spark plugs damaged on removal and diagnosed four faulty fuel injectors, replacing the full set. In the second, the dealer found active misfires on two cylinders, with dark grey smoke and a sulfur smell from the exhaust and shaking severe enough to crack the engine cover. This is separate from the 24V763000 high-pressure fuel pump recall — the failing component here is the direct injectors themselves, and the fuel-trim disturbance shows up as fouled plugs rather than a leak.
Common Symptoms
- Sudden rough idle and shaking at startup on a near-new car
- Active misfires on multiple cylinders
- Fuel-fouled or damaged spark plugs on removal
- Dark grey exhaust smoke and sulfur smell
- Shaking severe enough to crack the engine cover
How to Fix
Scan for misfire codes (P0300 plus the cylinder-specific P0301-P0304) and have the dealer perform an injector balance/leak-down test before parts are thrown at it — a wet, fuel-fouled plug on a cylinder with a leaking injector is the diagnostic tell. Have the dealer confirm the high-pressure fuel pump recall 24V763000 status on the same visit, since fuel-pressure faults can present similarly.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (3)
Ignition coil packs can fail causing engine misfires. Usually one coil fails at a time, causing a misfire, rough idle and a check engine light with misfire codes. Replacement is an easy DIY job (bolt on, connector plug) that saves $100-200 in shop labor.
Common Symptoms
- Engine misfire
- Rough idle
- Check engine light with misfire codes P0300-P0304
- Reduced fuel economy
- Hesitation during acceleration
How to Fix
Test coil pack resistance with multimeter before replacing to confirm failure. On 2015 Fits built December 2013 to August 2014, check the VIN for recall 15V-559 - dealers replace the plug-top ignition coils with a new design free. Replace failed ignition coil pack. Consider replacing all four if one fails ($200-300 for all four) to prevent future failures and repeated labor costs. FitFreak members recommend Bosch ($50-80 each) or Denso ($60-90 each) coils. DIY installation very easy.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Honda 30520-PWC-S01 ignition coilOEMHonda 30520-PWC-S01
First-generation replacement after diagnosis identifies a failed coil Fitment/availability: 2007-2008 U.S. Honda Fit Base and Sport, 5MT or 5AT; one coil per cylinder.
- Genuine Honda 30520-RB0-S01 ignition coilOEMHonda 30520-RB0-S01
Second-generation replacement after diagnosis identifies a failed coil Fitment/availability: 2009-2013 U.S. Honda Fit Base/Fit and Sport, 5MT or 5AT; one coil per cylinder.
- Genuine Honda 30520-5R0-013 ignition coilOEMHonda 30520-5R0-013
Third-generation replacement after diagnosis identifies a failed coil Fitment/availability: 2015-2020 U.S. Honda Fit, all cataloged trims, 6MT or CVT; one coil per cylinder.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipReplace all four at once ($200-300) to prevent future failures and repeated labor costs
- TipDIY installation is very easy - bolt on, connector plug - saves $100-200 in shop labor
- WarningAvoid knockoff coils on eBay/Amazon - they fail quickly and waste money
Sources for this issue (2)
Rough or fluctuating idle, stalling at traffic lights, low idle RPM (below 500 RPM). Often related to carbon buildup in throttle body or PCV system problems. DIY throttle body cleaning resolves 80% of idle issues according to FitFreak forums. Seafoam fuel system cleaner ($12-15) poured into fuel tank is popular preventive maintenance. Gumout carburetor cleaner ($10-15) works well for intake valve cleaning.
Common Symptoms
- Rough or fluctuating idle
- Stalling at traffic lights or stop signs
- Low idle RPM (below 500)
- Multiple stalls in one drive cycle
- Engine shakes at idle
How to Fix
Clean throttle body and intake valve carbon ($100-200 DIY with cleaner, $200-400 shop). Check and clean PCV system. Replace air filter if clogged. Fuel injector cleaning. Seafoam fuel system cleaner ($12-15) or Chevron Techron ($8-12) in fuel tank. Gumout carburetor cleaner ($10-15) for intake valves.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Honda 17130-PND-A01 PCV valveOEMHonda 17130-PND-A01
PCV branch only after inspection or testing confirms a stuck, clogged or damaged PCV valve Fitment/availability: 2009-2013 and 2015-2020 U.S.
- Genuine Honda 17220-RB0-000 engine air filterOEMHonda 17220-RB0-000
Early-generation filter branch after inspection confirms restriction, damage or overdue maintenance Fitment/availability: 2009-2013 U.S.
- Genuine Honda 17220-5R0-008 engine air filterOEMHonda 17220-5R0-008
Late-generation filter branch after inspection confirms restriction, damage or overdue maintenance Fitment/availability: 2015-2020 U.S.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipDIY throttle body cleaning resolves 80% of idle issues according to FitFreak - simple $15-50 fix in supplies
- TipCheck and clean PCV system - helps with oil consumption AND idle issues for $10-20 in supplies
Sources for this issue (2)
Owners of the 2006-2010 Ridgeline's 3.5L J35 V6 have reported spark plugs that loosened and blew out of the aluminum cylinder head while driving. One 2007 owner reported that at 67,442 miles, on the highway at 70 mph, "the spark plug blew out of the engine head in two pieces" and took the ignition coil with it. They said no check engine light came on first, and they were quoted $12,048.85 for the repairs. In another 2007 report, at 124,000 miles, the engine made an abnormal noise at about 55 mph. A technician then found that a spark plug had fractured and fallen into the engine, and the engine had to be replaced. Honda's specified spark plug torque for this engine is 18 N·m (13 lb-ft). We found no Honda service bulletin or recall for this problem.
Common Symptoms
- Misfire codes P0300-P0306 and a check engine light
- Rough idle or hesitation
- Abnormal engine noise while driving
- A plug and its ignition coil are blown out of the cylinder head while driving, sometimes with no warning light beforehand
- Damaged ignition coil after a plug blows out
- Severe engine damage if a broken plug falls into the cylinder
How to Fix
If you get a misfire code (P0300-P0306), the engine runs rough, or you hear a new noise from the engine, have the spark plugs checked before you drive hard again. Remove each ignition coil and check whether any plug is loose. If a plug is loose and the threads are still good, tighten it to Honda's spec of 18 N·m (13 lb-ft) with a torque wrench, not to 18 lb-ft. Use the same torque wrench and spec whenever you replace the plugs. If a plug has already blown out or broken, have a shop inspect the threads in the cylinder head and check the cylinder for pieces of the plug before the engine is run again. We found no recall, bulletin or warranty extension that covers this problem.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Honda / NGK 9807B-5517W IZFR5K11 spark plug, quantity oneOEMHonda 9807B-5517W / NGK IZFR5K11
exact early spark-plug replacement after inspection confirms plug replacement is due or required Fitment/availability: 2006-2008 U.S.
- Genuine Honda / NGK 12290-R70-A01 ILZKR7B11 spark plug, quantity oneOEMHonda 12290-R70-A01 / NGK ILZKR7B11
exact later spark-plug replacement after inspection confirms plug replacement is due or required Fitment/availability: 2009-2010 U.S.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipUse torque wrench when installing spark plugs - do not over-tighten (18 ft-lbs spec exactly)
- TipAlways work on engine when completely cool - aluminum expands significantly when hot and causes incorrect torque readings
- TipCheck spark plug torque at 60,000 miles and every 30,000 miles thereafter as preventive maintenance
- WarningHave coil packs inspected immediately if misfire codes appear - replacing coils early prevents catastrophic $4,000+ engine damage
Sources for this issue (4)
P0302 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0302 mean on a Honda?
P0302 stands for "Cylinder 2 Misfire Detected." This code means the engine computer has detected a misfire specifically in cylinder 2, meaning that cylinder isn't completing combustion properly on some firing events. The computer watches tiny variations in crankshaft speed to spot when a cylinder fails to fire, and a misfire means the air-fuel mixture isn't igniting correctly — usually from a spark, fuel, or compression problem in that cylinder. You may feel a stumble, rough idle, shaking, loss of power, or a flashing check-engine light, and persistent misfires can damage the catalytic converter. Because it names a single cylinder, the fault is often a component serving just cylinder 2, like its coil, plug, or injector. On Honda it is documented across 8 models: Civic, Fit, Ridgeline, Pilot, CR-V, Insight, Crosstour, Passport.
What are the most common causes of P0302?
The most common causes of P0302 are: Worn or fouled spark plug (cylinder 2), Failed ignition coil or coil-on-plug (cylinder 2), Clogged or faulty fuel injector (cylinder 2), Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt/bent valve, head gasket), Damaged spark plug wire or boot (if equipped), Carbon-tracked or cracked coil/plug causing spark loss, Faulty PCM/ECM driver (rare). The specific cause varies by vehicle.
How much does it cost to fix P0302 on a Honda?
Published repair estimates on Honda range from $20 to $8,000 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.