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In general, an OBD-II Code P0171 means that a long term lean condition ahs been detected at bank 1 , oxygen sensor 1.
This can have many causes, from a failing oxygen sensor, to a restricted fuel filter, failing fuel pump, vacuum leak, high electrical resistance in the front O2 sensor circuit, or many other causes. the code doesnt tell you what part to replace, you have to do some diagnostic testing to isolate the cause.
Here is a link you may find useful; if gives you definitions for many generic automotiive fault codes:
I hope this is helpful; if so, clicking mya ccept button would be most appreciated! Thanks!
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