P0172 on a Honda: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

You can drive short-term, but the rich mixture wastes fuel and can damage the catalytic converter, so get it checked soon.

What P0172 means on a Honda

On a Honda, P0172 means bank 1 is running rich — too much fuel or not enough air in the mixture. The Honda engine computer has already removed as much fuel as it can and still sees a rich mixture, so it sets the code.

Is P0172 common on Hondas?

P0172 appears on Hondas with higher mileage, most often on the Civic, Accord, and CR-V. Aging oxygen sensors are a common Honda wear item, and a contaminated MAF sensor is another frequent cause. Leaking fuel injectors can also push the mixture rich.

Commonly reported on: Civic, Accord, CR-V, Pilot.

Symptoms

Check engine light on
Poor fuel economy
Strong fuel smell from the exhaust
Rough idle

Common causes

most common: Aging or faulty oxygen sensor
common: Contaminated or failing MAF sensor
common: Leaking fuel injector
less common: Faulty fuel pressure regulator holding pressure too high
less common: Restricted air filter or intake

How to fix it

Fix	DIY?	Typical cost
Replace the faulty oxygen sensor	Yes	$60–200
Clean or replace the MAF sensor	Yes	$10–300
Replace leaking fuel injectors or the pressure regulator	Mechanic	$150–500