P0430 on Honda: How to Diagnose & Fix
Catalyst System Efficiency Below Threshold (Bank 2)
4 Honda models · 5 documented issues · 2 critical · $81-$3,500 repair
P0430 on Honda by model: symptoms, diagnosis and fix
Variable Cylinder Management (VCM) deactivates 3 rear cylinders during light load, but insufficient pressure allows oil to bypass the piston rings into the combustion chamber. Causes excessive oil consumption (1 quart per 1,000 miles), fouled spark plugs, catalytic converter damage, and premature piston ring wear. Honda settled a class-action lawsuit over the problem.
Common Symptoms
- Excessive oil consumption (1 qt per 1,000 miles or more)
- Engine misfire codes (P0300-P0304, typically cylinders 1-4)
- Fouled/oil-soaked spark plugs
- Rough idle and vibration
- Check engine light (misfire and catalyst codes)
- White smoke from exhaust on startup
- Failed catalytic converters (P0420/P0430)
How to Fix
Install VCM disable device (VCMuzzler, VCMTuner) which prevents cylinder deactivation and stops oil consumption. Replace fouled spark plugs after installing disabler. Honda settled a class action (Soto v. American Honda) covering 2008-2013 Odyssey with an 8-year warranty extension for engine misfire repairs, and announced a further warranty extension in June 2025 for certain 2013-2017 Odyssey. Severe cases may require piston ring replacement ($3,000-$5,000). 2014-2017 models still use VCM.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Honda/NGK 9807B-5517W IZFR5K11 spark plug, eachOEMHonda 9807B-5517W / NGK IZFR5K11
Early-generation plug branch only after inspection identifies a fouled plug and exact catalog application Fitment/availability: 2005-2007 U.S. Honda Odyssey 3.5L applications in this issue; Honda catalogs 9807B-5517W across 2005-2010 but…
- Genuine Honda/NGK 12290-R70-A01 ILZKR7B11 spark plug, eachOEMHonda 12290-R70-A01 / NGK ILZKR7B11
VCM plug-fouling branch after code and plug inspection identifies replacement Fitment/availability: 2008-2010 U.S. Honda Odyssey EX-L/Touring with VCM; select 12290-R70-A01.
- Genuine Honda/NGK 12290-R71-L01 DILZKR7A11G spark plug, eachOEMHonda 12290-R71-L01 / NGK DILZKR7A11G
Fourth-generation plug-fouling branch after P0301-P0304 and physical plug diagnosis Fitment/availability: 2011-2017 U.S. Honda Odyssey all trims; sold individually and six are required for a full set.
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Owner tips & cautions
- TipCheck oil level every fuel fill-up on VCM-equipped models - carry a quart of oil in the van
- WarningDon't ignore misfire codes - prolonged misfires destroy catalytic converters ($2,000+ repair)
Sources for this issue (2)
The 8th generation Accord V6 (3.5L J35Z2) with Variable Cylinder Management (VCM) deactivates 3 cylinders at highway speeds, causing excessive oil consumption (1 quart per 1,000-1,500 miles), misfires, and accelerated engine vibration that damages engine mounts. When VCM deactivates cylinders, insufficient ring pressure allows oil to bypass rings into combustion chamber. The class action lawsuit (Soto v. American Honda, filed 2012) covered about 1.6 million VCM vehicles. Honda settled in 2013, providing an 8-year, unlimited-mileage extended warranty for repairs related to VCM-caused misfires and spark plug fouling. Many owners in the Drive Accord community disable VCM immediately upon purchase.
Common Symptoms
- Oil level dropping about 1 quart every 1,000-1,500 miles
- Engine misfires (P0300-P0306 codes)
- Fouled spark plugs with carbon and oil deposits
- Excessive vibration felt through steering wheel and seats
- Check engine light with misfire and/or catalyst codes
- Catalytic converter efficiency codes (P0420, P0430)
- Blue smoke from exhaust at startup
How to Fix
Install VCM disabler device: VCMuzzler II (~$81, simplest install, no power wire), VCMTuner II ($150-200, more features), or S-VCM Controller ($180-250, automatic temperature adjustment). Check oil every 500-1,000 miles until VCM disabled. Replace fouled spark plugs with NGK DILKAR7B11 ($5-8 each) every 30,000-50,000 miles. Honda's 2013 class action settlement provided an 8-year extended warranty for misfires with fouled plugs - contact Honda with VIN (the 8-year term has now run out on most cars). Severe cases (catalytic converters destroyed): $2,000-3,500 replacement.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- VCMuzzler II VCM suppression deviceOEMVCMuzzler II
Optional owner-selected VCM suppression after understanding the device's operating tradeoffs Fitment/availability: 2008-2012 Accord V6 automatic only; vendor explicitly excludes manual-transmission Accord. Select model year, model and pi…
- S-VCM ControllerOEMS-VCM Controller
Confirm connector/application with vendor.
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Sources for this issue (2)
Accords are a frequent source of P0420 (Bank 1 catalyst below threshold) and, on the J-series V6 with its dual converters, P0430 (Bank 2). While high-mileage catalyst aging is normal, on these cars failures are often accelerated by upstream oil consumption — the K24 sticking-piston-ring oil burn and the V6 VCM oil consumption saturate and poison the catalyst — so a 'bad cat' code is often a symptom of an oil-control problem. A lazy downstream O2 sensor mimics the same code and wastes a cat replacement if not ruled out first.
Common Symptoms
- Check engine light with P0420 or P0430
- Failed emissions/smog test
- Sluggish acceleration or reduced fuel economy
- Rotten-egg/sulfur smell
- Often paired with oil consumption on K24/V6
How to Fix
Do not blindly replace the converter. First verify no misfire, no excessive oil consumption, and confirm the rear (downstream) O2/AFR sensor is healthy with live data — a slow-switching rear sensor causes false P0420. If oil consumption is the root cause, fix that first or the new cat will fail again. If the catalyst is genuinely spent, replace with an OEM or CARB-compliant direct-fit converter (V6 requires the correct bank). OEM converters are expensive; quality aftermarket units cost far less.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Walker CalCat 84292 rear direct-fit catalytic converterOEMWalker 84292
Replace a confirmed rear catalyst failure on the matching early K24 emissions branch Fitment/availability: 2008 Accord 2.4L only when the under-hood label shows EFN 8HNXV02.4TKR and the failed unit is the rear converter.
- Walker CalCat 84177 front direct-fit catalytic converterOEMWalker 84177
Replace a confirmed front catalyst failure on the matching eighth-generation K24 emissions branch Fitment/availability: 2010 Accord 2.4L only when the under-hood label shows EFN AHNXV02.4MB3 and the failed unit is the front converter.
- Walker CalCat 84171 front direct-fit catalytic converterOEMWalker 84171
Replace a confirmed front catalyst failure on the matching ninth-generation K24 emissions branch Fitment/availability: 2013 Accord 2.4L only when the under-hood label shows EFN DHNXV02.4FB3 and the failed unit is the front converter.
- Muffler Express 2008-2017 Accord 3.5L bank-1 direct-fit converterOEMMuffler Express bank 1 direct-fit
Replace a diagnosed bank-1 converter on the V6 branch Fitment/availability: 2008-2017 Accord 3.5L V6, bank 1 only, after verifying the seller's fitment, the vehicle EFN and local emissions legality. The seller does not represent this sta…
- Muffler Express 2008-2017 Accord 3.5L bank-2 direct-fit converterOEMMuffler Express 07-1-0029.0-1
Replace a diagnosed bank-2 converter on the V6 branch Fitment/availability: 2008-2017 Accord 3.5L V6, bank 2/radiator-side only, after verifying the seller's fitment, the vehicle EFN and local emissions legality.
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Sources for this issue (3)
The PCM software may misinterpret sensor inputs as a deteriorated catalytic converter, and debris from the high-pressure pump or the injector machining process can cause internal wear or clogging inside one or more fuel injectors. P0420/P0430, P0300-P0306 and P219A/P219B may be stored. 2016-2017 Pilot (bulletin 20-100, with software update) and 2017-2019 Pilot (bulletin 21-010, without software update), all trims, eligibility by VIN.
How to Fix
Have a Honda dealer verify the VIN and stored codes against 20-100 (2016–2017 Pilot, with software update) or 21-010 (2017–2019, without that update); the bulletins require at least 5,000 miles. With only P0420/P0430, perform the cylinder air-fuel test and replace the injectors only if it fails; 20-100 also requires its software update. With the specified misfire or air-fuel imbalance codes, follow the injector-replacement branch and any applicable software update. For a 9-speed automatic under 20-100, also confirm its A/T software is current. Use the complete specified fuel-injector kit (06160-RLV-305 in these bulletin versions), including all must-replace parts, rather than only the six injectors pictured. Honda’s extension is 10 years from original purchase or 150,000 miles, whichever comes first, with eligibility confirmed by the dealer. These sources do not direct automatic catalytic-converter replacement. If none of the listed codes is present, continue normal troubleshooting.
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 (4)
- Honda Service Bulletin 20-100, Warranty Extension: MIL Comes On with DTC P0420/P0430, P030x, and/or P219A/B (With Software Update) (Version 2, February 11, 2021)tsb
- Honda Service Bulletin 21-010, Warranty Extension: MIL Comes On with DTC P0420/P0430, P030x, and/or P219A/B (Without Software Update) (February 11, 2021)tsb
- Honda owner letter: Warranty Extension (Without Software Update) for 2017-19 Pilot fuel injectorstsb
- Honda dealer notice: Warranty Extension: 2016 Pilot V6 Fuel Injectortsb
The 3.2L V6 used in the first-generation Passport is known to develop exhaust leaks from broken manifold studs or warped manifold sealing surfaces as the vehicle ages. Owners commonly describe a ticking noise on cold start, exhaust smell, and occasional failed emissions testing. Heat cycling and corrosion are the usual causes, and the repair can become labor-intensive if studs snap flush in the cylinder head.
Common Symptoms
- ticking noise on cold start
- exhaust smell in engine bay
- soot around exhaust manifold
- louder exhaust under acceleration
- failed emissions inspection
How to Fix
Confirm the leak with a cold-start inspection, smoke test, or by checking for soot around the manifold flange and studs. Replace broken studs, resurface or replace the manifold if warped, and install new gaskets and hardware. Penetrating oil, heat, and careful extraction are often required to avoid cylinder-head damage.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Fel-Pro MS90725 exhaust-manifold gasket setOEMFel-Pro MS90725
Head-to-manifold sealing branch after the leaking bank is confirmed and the manifold is removed for stud repair or replacement Fitment/availability: 2000-2002 U.S. Honda Passport 3.2L V6 within this issue; select Fel-Pro MS 90725 and re-…
Sources for this issue (1)
P0430 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 P0430 mean on a Honda?
P0430 stands for "Catalyst System Efficiency Below Threshold (Bank 2)." This code means the catalytic converter on Bank 2 (the side of the engine that does not contain cylinder #1) is not reducing emissions as effectively as it should. The computer compares the readings of the oxygen sensors before and after the converter; if the downstream sensor's signal starts mirroring the upstream one, it indicates the converter is no longer storing and processing oxygen properly. This usually points to a worn-out or damaged catalytic converter, but it can also be caused by faulty sensors or upstream engine problems that have poisoned the converter. The car will generally still run, but it will fail an emissions test. On Honda it is documented across 4 models: Odyssey, Accord, Pilot, Passport.
What are the most common causes of P0430?
The most common causes of P0430 are: Worn-out or failed catalytic converter (Bank 2), Faulty downstream (post-cat) oxygen sensor, Faulty upstream oxygen sensor giving bad data, Exhaust leak near the converter or sensors, Engine misfire or oil/coolant burning that damaged the catalyst, Running too rich or too lean over time, Aftermarket or non-compliant catalytic converter. The specific cause varies by vehicle.
How much does it cost to fix P0430 on a Honda?
Published repair estimates on Honda range from $81 to $3,500 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.