P0174 on Honda: How to Diagnose & Fix
System Too Lean (Bank 2)
11 Honda models · 14 documented issues · 8 critical · $20-$8,000 repair
P0174 on Honda by model: symptoms, diagnosis and fix
Gasoline mixes with engine oil in the 1.5L turbocharged engine, causing the oil level to rise above the full mark. The issue is most prevalent in cold climates where short trips don't allow the engine to reach full operating temperature. Unburned fuel bypasses the piston rings and enters the crankcase, diluting the oil and reducing its lubricating properties.
Common Symptoms
- Oil level reading above full mark on dipstick
- Strong gasoline smell from engine oil
- Check engine light illumination
- Reduced engine power
- Engine stalling
- Poor fuel economy
How to Fix
Honda released a software update (PCM update) that raises engine operating temperatures faster and increases idle RPM in cold conditions. For 2017-2018 models, Honda also extended the powertrain warranty by one year. Owners should change oil more frequently (every 3,000-5,000 miles) in cold climates.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Honda 15400-PLM-A02 engine oil filterOEMHonda 15400-PLM-A02
Oil-filter consumable when an owner performs the shorter oil-change interval described by the repair guidance Fitment/availability: 2017-2023 U.S. CR-V 1.5T within this record; cataloged broadly for the CR-V and shown specifically for th…
Owner tips & cautions
- WarningThis is a high-severity issue - ignoring it can lead to costly repairs or safety concerns. Address it promptly.
- TipGet a proper diagnosis before replacing parts - similar symptoms can have different causes
- TipSearch Honda CR-V forums and owner groups for real-world experiences and DIY guides
- TipGet multiple quotes from independent mechanics - dealer prices can be 2-3x higher for the same repair
Sources for this issue (3)
Variable Cylinder Management (VCM) deactivates 3 rear cylinders during light load, but insufficient pressure allows oil to bypass piston rings into 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 class-action lawsuit covering 1.6-1.87 million vehicles.
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 class-action providing 8-year warranty extension for engine misfire repairs. Severe cases may require piston ring replacement ($3,000-$5,000). 2014+ models received redesigned engine without 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.
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
- 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)
Variable Cylinder Management (VCM) causes excessive oil consumption (1 quart every 1,000-1,500 miles), engine misfires, and fouled spark plugs. The reciprocating effect creates vacuum that pulls oil past piston rings. Leads to premature failure of spark plugs, catalytic converters, engine mounts, and cylinder walls. 2013 class action lawsuit identified 1.6 million affected vehicles.
Common Symptoms
- Excessive oil consumption (1 qt per 1,000-1,500 miles)
- Engine misfires (P0300-P0306 codes)
- Fouled spark plugs
- Rough idle or hesitation
- Check engine light
- Excessive engine vibration when VCM activates
- Blue smoke from exhaust
How to Fix
Disable VCM using aftermarket devices: VCMuzzler II ($81), VCMTuner II ($150-200), or S-VCM Controller ($180-250). Check oil level every 500-1,000 miles and top off as needed. Use synthetic 0W-20 oil. Replace spark plugs every 30k-50k miles instead of 100k. Severe cases may need engine rebuild ($4,000-$8,000).
Owner tips & cautions
- TipDisabling VCM reduces damage to engine mounts ($800) and minimizes transmission torque converter wear
- TipCheck oil level every 500-1,000 miles and keep 2-3 quarts of oil in vehicle for top-offs
- WarningDo not ignore excessive oil consumption - running engine low on oil can cause catastrophic engine failure
Sources for this issue (1)
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 (Rodriguez v. American Honda, 2013) covered 1.87 million vehicles. Honda settled in 2016 providing extended warranty for engine repairs related to VCM-caused misfires and oil consumption. Many owners in the Drive Accord community disable VCM immediately upon purchase.
Common Symptoms
- Oil level dropping 1-2 quarts between 3,000-5,000 mile oil changes
- 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 2016 class action settlement may provide extended warranty for misfires/consumption - contact Honda with VIN. 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.
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)
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)
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)
P0174 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 P0174 mean on a Honda?
P0174 stands for "System Too Lean (Bank 2)." P0174 means the engine computer detected that the air-fuel mixture on Bank 2 (the side of the engine with cylinder 2) is running too lean — too much air relative to fuel. The computer monitors this through the oxygen/air-fuel sensors and fuel trims; when it has to add a large amount of extra fuel to compensate and still can't reach the target, it flags the mixture as too lean. A lean condition can cause rough idle, hesitation, or misfires, and over time can raise combustion temperatures. Because it's Bank 2 specific, an unmetered air leak on that bank or a fuel delivery shortfall is typical. On Honda it is documented across 11 models: CR-V, Odyssey, Pilot, Accord, Civic, Ridgeline, Fit, S2000, Element, Insight, Crosstour.
What are the most common causes of P0174?
The most common causes of P0174 are: Vacuum or intake air leak (hoses, gaskets, PCV), Dirty or failing mass airflow (MAF) sensor, Weak fuel pump or restricted fuel filter (low fuel pressure), Clogged or underperforming fuel injectors, Leaking intake manifold or throttle body gasket, Faulty or contaminated oxygen / air-fuel sensor, Exhaust leak upstream of the oxygen sensor, Stuck-open EGR valve. The specific cause varies by vehicle.
How much does it cost to fix P0174 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 P0174 on a different make?
View P0174 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.