P0172 on Mazda: How to Diagnose & Fix
System Too Rich (Bank 1)
1 Mazda model · 1 documented issue · 1 critical
P0172 on Mazda by model: symptoms, diagnosis and fix
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.
Common Symptoms
- Fuel smell or visible fuel leak from rear of vehicle after a full tank fill-up
- Engine stalls while driving
- Liquid fuel overflowing the EVAP charcoal canister
- Emissions/check-engine warning
How to Fix
Recall 20V347000 (Mazda campaign 4520F) covers ~12,097 AWD vehicles. Dealers inspect the evaporative vent hose in the fuel tank, reconnect it if disconnected, and replace the charcoal canister and related parts, free of charge. Recall began July 29, 2020.
Sources for this issue (3)
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 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 it is documented across 1 model: CX-30.
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 Mazda?
Repair costs vary widely with the root cause and Mazda 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.