P0172 on Mazda
System Too Rich (Bank 1)
P0172 on Mazda vehicles indicates system too rich (bank 1). Au7o has documented this code across 1 Mazda model — most commonly on CX-30. 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 Mazda by Model
Mazda CX-30(1 issue)
- Disconnected Fuel Evap Vent Hose Causing Fuel Leak / Stalling (AWD) - Recall 20V347000 (4520F)2020
On 2020 CX-30 AWD models, the fuel evaporative vent hose may be disconnected from the fuel sender unit due to a fuel-tank plant manufacturing error. After a full fill-up, liquid fuel can flood the charcoal canister and leak from the rear of the vehicle, creating a fire risk near an ignition source; the engine can also stall while driving.
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View P0172 across all makes →Frequently Asked Questions
What does P0172 mean on Mazda?▼
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 Mazda specifically, this code is documented across 1 model.
What causes P0172 on Mazda vehicles?▼
Common causes on Mazda: 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 Mazda?▼
Repair costs vary widely depending on the root cause and specific Mazda model.
Which Mazda models have P0172 documented?▼
Au7o has documented P0172 on 1 Mazda model: CX-30.