System Too Rich (Bank 1)
Powertrain Code · Medium
What does P0172 mean?
The engine is running rich on bank 1 — too much fuel or not enough air. Common causes include leaky fuel injectors, stuck-open purge valve, or a dirty/faulty MAF sensor.
System: Fuel System
P0172 is a powertrain diagnostic trouble code indicating system too rich (bank 1). This code is classified as medium severity, which means: schedule service — affects performance or emissions. We have vehicle-specific diagnostic data for 43 models below. Select your vehicle for tailored causes, symptoms, and repair cost estimates.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your vehicle.
See causes, symptoms, and repair costs for P0172 on specific vehicles: