An OBD II error code PO171 means that the oxygen sensor located in bank one is producing too much oxygen in the car's exhaust system. Additionally, this error code indicates that the powertrain and engine control module are unable to regulate the proper ratio of fuel to air.
This diagnostic trouble code is a common OBD II powertrain code. In vehicles made after 1996, this trouble code carries the same meaning for all models and makes of vehicles in the United States.
OBD is an acronym for On Board Diagnostics and was created by the Society of Automotive Engineers and the International Standardization Organization. OBD is designed to decrease vehicle emissions by reporting performance issues of major engine components.