P0172 on Honda: How to Diagnose & Fix
System Too Rich (Bank 1)
1 Honda model · 1 documented issue · 1 critical
P0172 on Honda by model: symptoms, diagnosis and fix
The fifth-gen CR-V's 1.5L 'Earth Dreams' turbo direct-injection engine (L15BE) is prone to gasoline diluting the engine oil, especially in cold-weather states and on short trips where the engine never fully warms. Under cold conditions the fuel injectors spray gasoline onto cylinder walls that doesn't fully combust; it then drips past the rings into the crankcase, raising the oil level well above the dipstick full mark and producing a strong fuel smell from the dipstick and sometimes in the cabin (via the heater). Diluted oil loses viscosity and lubrication capacity, accelerating wear on camshafts, rocker arms, and bearings. The problem was significant enough to trigger a nationwide class-action settlement (District of Minnesota, final approval Sept 2020) covering 2017-2018 CR-V and 2016-2018 Civic 1.5T, plus a Honda powertrain warranty extension. CarComplaints logged 89 complaints on the 2017 and 60+ on the 2018 with very low average mileage (~8,400 mi).
Common Symptoms
- Engine oil level rises above the dipstick full mark over time
- Strong gasoline smell on the dipstick
- Fuel/gasoline odor inside the cabin, especially with heat on
- Engine hesitation or stalling in cold weather
- Weak cabin heat in cold temperatures
- Thin, fuel-smelling oil at oil changes
How to Fix
Honda's remedy (TSB 19-032 / 19-037 / 19-038) is a software update to the engine, transmission, and A/C control logic so the engine warms faster and runs richer for less time, an oil-and-filter change, and in some cases replacement of the A/C control unit. Honda extended the powertrain warranty on camshafts/rocker arms to 6 years/unlimited miles. There is no full mechanical fix — owners in cold climates should change oil more often, take the car on longer drives to burn off fuel, and monitor the dipstick. The class settlement reimburses prior premature oil changes, towing, and diagnostic costs.
Sources for this issue (3)
- Warranty Extension TSB 19-032 — 2017-18 CR-V: Software Update with A/C Control Unit Replacement; DTC P0300-P0304/P0172 (NHTSA bulletin PDF)tsb
- Judge Approves Honda Oil Dilution Class Action Settlement (2017-2018 CR-V & 2016-2018 Civic 1.5T)article
- 2018 Honda CR-V Fuel In Oil With Overfilled Oil Level, Gas Smell In Cabin (CarComplaints — 63 complaints)forum
P0172 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 P0172 mean on a Honda?
P0172 stands for "System Too Rich (Bank 1)." P0172 means the engine computer has determined the air/fuel mixture on bank 1 is too rich — there is too much fuel relative to air. The PCM watches the oxygen sensors and fuel trims; when it must repeatedly cut back fuel to compensate for an over-rich condition and hits its correction limit, it sets this code. Bank 1 is the side of the engine containing cylinder number one. You may notice poor fuel economy, rough idle, a sulfur/rotten-egg smell, black exhaust smoke, or fouled spark plugs. On Honda it is documented across 1 model: CR-V.
What are the most common causes of P0172?
The most common causes of P0172 are: Dirty or faulty mass airflow (MAF) sensor, Leaking or stuck fuel injector, High fuel pressure (faulty regulator), Faulty oxygen sensor giving skewed readings, Clogged or dirty air filter, Leaking evaporative purge valve adding fuel vapor, Engine coolant temperature sensor reading too cold, Worn spark plugs causing inefficient combustion. The specific cause varies by vehicle.
How much does it cost to fix P0172 on a Honda?
Repair costs vary widely with the root cause and Honda model; each issue on this page carries its own estimate where one is published.
Looking for P0172 on a different make?
View P0172 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.