OBD codes / P0171
P0171
SeriousSystem Too Lean (Bank 1)
Address promptly — can worsen or affect drivability.
Likely causes
- vacuum/intake leak
- dirty MAF
- weak fuel pump
- clogged filter
Common fixes
- smoke test for leaks
- clean MAF
- check fuel pressure
Seeing P0171 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0171 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.