I have the same code p0174 and also it said, "poor system" on 2003 Ford Windstar

What is that?

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1 answer
P0174 (bank 2)indicates that your air/fuel mixture is too lean. There is more air/oxygen than there is fuel.

Typically lean running conditions can be caused by vacuum leaks, insufficient flow/pressuure from fuel pump, fuel line clogged or leaking, fuel pressure regulator stuck open, fuel filter clogged, fuel injectors clogged, gasoline quality (poor), bad primary oxygen sensor, valve clearances and exhaust leak.

I would start out with the easiest possible cause: vacuum leaks.