P0171: System Too Lean (Bank 1)
System: Fuel trim · Priority: medium
What P0171 means
The control module detected a condition matching the generic definition System Too Lean (Bank 1). A trouble code identifies what the module detected; it does not automatically identify the failed part.
Useful next checks
- Inspect for vacuum or intake leaks.
- Check fuel pressure and injector delivery if trims stay lean under load.
- Review short- and long-term fuel trims with live data.
Why vehicle context matters
The same generic code can have different diagnostic paths depending on engine, calibration, wiring layout, service bulletins and related codes. Freeze-frame and live data can help establish when the fault occurred.
Need a scanner for P0171?
Build a direct VeroRoad page for your year, make and model. It will open the vehicle-specific read-codes / diagnostic context instead of a generic product list.