The check engine light comes on my 2002 Kia Optima and diagnostic was ran the code P0171 came up what does this mean?

The P0171 code indicates that the air/fuel mixture in the engine is too lean. This means that there is not enough fuel being mixed with the air in the combustion chamber. This can cause the engine to run rough, stall, or have reduced fuel efficiency.

There are several possible causes for this code, including:

A dirty or faulty mass air flow (MAF) sensor.

A dirty or faulty oxygen sensor.

A vacuum leak in the engine.

A fuel injector that is not working properly.

To find the cause of the P0171 code, you will need to perform some additional diagnostics. This may include visually inspecting the engine for vacuum leaks, cleaning the MAF sensor and oxygen sensor, and testing the fuel injectors. If you are not comfortable performing these diagnostics, you should take your car to a qualified mechanic.