P0302 on Honda: How to Diagnose & Fix
Cylinder 2 Misfire Detected
9 Honda models · 17 documented issues · 7 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 (LX through Si). Honda addressed this in 11th gen with port+direct injection (GDI).
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 …
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
- 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)
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. Replacement injectors and plugs are covered under Honda's 3-year/36,000-mile new-vehicle warranty and the 8-year/80,000-mile federal emissions warranty; do not accept a plugs-only repair, because new plugs on a leaking injector will foul again within weeks. 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 (1)
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.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (1)
2016-2018 Pilots suffer from debris in direct-injection fuel system causing internal wear or clogging inside injectors. Causes misfire codes (P0300-P0306), catalyst efficiency codes (P219A/B, P0420/P0430), rough idle, and stalling. TSB 20-100 addresses this defect. Honda extended warranty to 10 years/150,000 miles for 2016-2017 models.
Common Symptoms
- Check engine light with misfire codes (P0300-P0306)
- Catalyst efficiency codes (P0420, P0430, P219A, P219B)
- Rough idle or engine stumbling
- Engine stalling at stops
- Poor fuel economy
- Fuel smell at idle
- Loss of power under acceleration
How to Fix
Visit Honda dealer for diagnosis using TSB 20-100. For vehicles with these codes, Honda will replace fuel injectors and catalytic converters under extended warranty (10 years/150,000 miles for 2016-2017). PCM software update also available. Keep documentation of all misfires and check engine lights to support warranty claim.
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 16010-RLV-315 six-piece fuel-injector setOEMHonda 16010-RLV-315
Retail fallback only after Honda warranty/VIN review and diagnosis confirm the injector branch Fitment/availability: 2016-2018 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
- TipHonda extended warranty to 10 years/150,000 miles for 2016-2017 models with these codes - document all issues
- TipIf dealer denies warranty claim, reference TSB 20-100 specifically and escalate to Honda corporate
- WarningDo not ignore misfire codes - continued driving can damage catalytic converters ($1,500-$3,500 to replace)
- WarningThese codes often misdiagnosed as VCM issues - verify with dealer using TSB 20-100 for correct diagnosis
Sources for this issue (2)
On the J35 V6, the rubber valve cover gaskets and the integrated spark plug tube seals harden and shrink with age and heat, allowing oil to weep onto the hot exhaust manifolds (burning-oil smell) and, more seriously, to pool down inside the spark plug wells. Oil saturates the ignition coil boots and shorts the spark, producing misfires and a Check Engine Light. The rear (firewall-side) bank is hardest to access, so the leak is often neglected until misfires appear.
Common Symptoms
- Burning oil smell from the engine bay
- Oily residue/grime on top of the valve covers
- Oil pooled in the spark plug wells
- Rough idle, misfire, and Check Engine Light
- Occasional blue smoke / slightly higher oil consumption
How to Fix
Replace both valve cover gaskets and the spark plug tube seals (gasket sets include the tube seals); clean oil from the spark plug wells and inspect/replace any oil-soaked ignition coil boots and fouled spark plugs. Parts are inexpensive ($40-$80 per set) but labor is significant on the rear bank.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Fel-Pro VS50773R complete valve-cover gasket setOEMFel-Pro VS50773R / PartsGeek 29982-05418108
Confirm package contents on arrival.
- Genuine Honda 12030-5G0-000 front head-cover gasket packageOEMHonda 12030-5G0-000
2016-2020 front/radiator-bank gasket and tube-seal branch Fitment/availability: 2016-2020 U.S. Honda Pilot 3.5L V6 front head cover; package includes the front cover gasket, tube seals and sealing washers.
- Genuine Honda 12050-5G0-000 rear head-cover gasket packageOEMHonda 12050-5G0-000
2016-2020 rear/firewall-bank gasket and tube-seal branch Fitment/availability: 2016-2020 U.S. Honda Pilot 3.5L V6 rear head cover; package includes the rear cover gasket, tube seals and screw grommets.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (2)
The 11th generation Accord 2.0T (K20C4 engine) inherited the direct-injection carbon buildup issue from the 10th gen. Without port injection to clean intake valves, carbon deposits accumulate on the intake valves and ports starting at 30,000-50,000 miles. The 2.0T engine is more susceptible than the 1.5T because it runs higher combustion temperatures. Additionally, the 11th gen Accord 2.0T reports an unusual idle vibration at cold start that owners describe as a "diesel-like" clatter lasting 2-5 seconds. Honda TSB 23-055 addresses this with an ECM calibration update that adjusts cold start timing.
Common Symptoms
- Rough idle or stumbling at cold start
- Diesel-like rattling or clatter for first few seconds of cold start
- Hesitation or stumbling under light throttle application
- Reduced fuel economy after 30,000+ miles
- Occasional misfires on cold mornings (P0300-P0304)
- Hard cold starts that require extended cranking
How to Fix
For cold start clatter: Visit Honda dealer for ECM calibration update per TSB 23-055 (free under warranty). For carbon buildup: Walnut blast cleaning every 40,000-60,000 miles ($300-500 independent shop). Use top-tier gasoline (Shell V-Power, Chevron, Costco Premium) which contains higher detergent additives. CRC GDI IVD Intake Valve Cleaner (#05319) spray treatment every 10,000 miles slows buildup. Oil catch can installation ($80-150) reduces PCV oil vapor contribution to carbon.
Sources for this issue (1)
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 9 models: Civic, Pilot, Accord, Fit, Ridgeline, Crosstour, Insight, CR-V, 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.
Looking for P0302 on a different make?
View P0302 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.