P0172 means the engine's air-fuel mixture on Bank 1 has too much fuel relative to air. The ECU detected that it cannot subtract enough fuel to maintain the correct 14.7:1 stoichiometric ratio, exceeding its negative fuel trim correction range.
DTC/P0172·Honda
P0172 on Honda: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Honda
P0172 on a Honda means the engine's air-fuel mixture on Bank 1 has too much fuel relative to air. The ECU detected that it cannot subtract enough fuel to maintain the correct 14.7:1 stoichiometric ratio, exceeding its negative fuel trim correction range.
Repair cost on Honda€7 - €315
What does P0172 mean on a Honda?
Honda Civic
2006-2024The 1.5L turbo in 2016+ Civics has a documented fuel dilution issue where gasoline mixes with engine oil. This can trigger P0172 as fuel-contaminated oil vapours re-enter the intake through the PCV system. Honda issued a software update to address the warm-up cycle.
What causes P0172 on a Honda?
Beyond the generic causes listed on the main P0172 page, these are the Honda-specific patterns we see most often:
Honda CivicFuel dilution in 1.5T causing oil vapour enrichment (2016+)
Honda CivicInjector seal degradation on R18A engines at high mileage
How to diagnose P0172 on a Honda with OBD2
Follow these steps to pinpoint the root cause of P0172:
- Check and replace air filter if clogged (cheapest fix first)
- Read live data: check STFT and LTFT at idle. Negative values beyond -8% confirm rich condition
- Rev to 2,500 RPM and hold. If trims return toward zero, cause is idle-specific (injector leak, purge valve). If trims stay negative, suspect MAF or fuel pressure
- Try unplugging the MAF sensor and driving briefly. If rich condition improves, clean or replace the MAF
- Check fuel pressure with a gauge. Compare to manufacturer spec at idle and under load
- Inspect EVAP purge valve for stuck-open condition
How much does P0172 cost to fix on a Honda? (EUR)
Estimated repair costs on a Honda (Honda parts and labour typically run 10% below the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0172 on Honda
These codes commonly cluster with P0172 on Honda vehicles:
FAQ: P0172 on Honda
Can I drive with a P0172 code?
Yes, short-term driving is generally safe. But a rich-running engine wastes fuel, can foul spark plugs, and over time damages the catalytic converter. Don't ignore it for weeks.
What is the most common cause of P0172?
A dirty or failing MAF sensor is the single most common cause. It misreads incoming air volume, causing the ECU to inject too much fuel. Cleaning the MAF sensor with dedicated MAF cleaner solves about 40% of P0172 cases.
Is P0172 the same as P0175?
They describe the same problem (too much fuel) but on different engine banks. P0172 is Bank 1, P0175 is Bank 2. If you have both codes, the cause likely affects the whole engine, like fuel pressure or a shared MAF sensor.
Can a dirty air filter cause P0172?
Yes. A severely clogged air filter restricts airflow, throwing off the MAF reading. Replace the air filter first. It costs under 15 euros and takes two minutes.
Looking for the full P0172 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0172 guideSkanyx · Honda
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