System Too Lean (Bank 1)
Powertrain Code · High
What does P0171 mean?
The engine is running lean on bank 1 — too much air or not enough fuel. Common causes include vacuum leaks, weak fuel pump, clogged fuel injectors, or a faulty MAF sensor.
System: Fuel System
P0171 is a powertrain diagnostic trouble code indicating system too lean (bank 1). This code is classified as high severity, which means: address soon — may cause further damage. We have vehicle-specific diagnostic data for 50 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 P0171 on specific vehicles: