Q: My car has a P0171 fuel system too lean code. The map sensor is ok at .95v, the fuel trim is at 122 and the 02 sensor is reading rich.

Hi there, thanks for writing in. The P0171 lean fuel system code can mean a variety of potential issues are at play, such as intake air leaks, a faulty front heated oxygen sensor, ignition misfiring, faulty fuel injectors, exhaust gas leaks, incorrect fuel pressure, lack of fuel, a faulty mass airflow sensor, or an incorrect positive crankcase ventilation (PCV) hose connection .

This depends on which O2 sensor is reading rich. There are often times two O2 sensors, one in front of the catalytic converter (pre-catalyst), which reads the oxygen levels prior to the conversion process and one after the catalytic converter (post catalyst) which reads the oxygen levels after the conversion process. If the O2 sensor after the catalytic converter is reading rich, this would suggest that the catalytic converter is not doing its job and may be clogged. I would recommend having an expert from Your Mechanic come to your home to diagnose and repair.

If you would like help with inspecting this code, consider having an expert automotive technician from YourMechanic come to your home or office to look at your car for you and diagnose the issue, and make any repairs, such as replacing your catalytic converter, if needed.