P0172 on Honda
System Too Rich (Bank 1)
P0172 on Honda vehicles indicates system too rich (bank 1). Au7o has documented this code across 1 Honda model — most commonly on CR-V. 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.
Common Causes of P0172
- •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
P0172 on Honda by Model
Honda CR-V(1 issue)
- 1.5L Turbo (L15BE) Engine Oil Dilution — Fuel in Oil, Overfilled Dipstick, Gas Smell in Cabin2017-2018
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).
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View P0172 across all makes →Frequently Asked Questions
What does P0172 mean on 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 specifically, this code is documented across 1 model.
What causes P0172 on Honda vehicles?▼
Common causes on Honda: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0172 on a Honda?▼
Repair costs vary widely depending on the root cause and specific Honda model.
Which Honda models have P0172 documented?▼
Au7o has documented P0172 on 1 Honda model: CR-V.