Need help code ERROR p0171 or code [51 in the haynes repair manual]

I just bought a [96 grand voyager 3.3L. V-6] and the check engine light is on. the major error/code is 51 or P0171. indicating: "A lean air/fuel mixture has been indicated by an abnormally rich
correction factor." what does that mean and how do I correct the malfunction?
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P0171 - Fuel system too lean, bank no.1
It means the engine is running lean. This could be caused by many things, such as a vacuum leak, low fuel pressure or a failed O2 sensor. It would be easily diagnosed with a scan tool ( not a code reader ) and fuel pressure guage.
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That is not a good fault code for that vehicle. (P0171) There is only one upstream 02 sensor for that engine and it will not determine front and rear lean/rich condition. Assuming that the engine is running good, (maybe a slight hesitation) and you are looking for a repair without having it properly diagnosed.....Replace the upstream 02 sensor. its probably the original one anyhow.
Glenn Beasley Chrysler Tech
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