Where is the oil pressure sending unit located on my 2004 Chrysler pacifica?

http://www.underhoodservice.com/servicing-the-chrysler-3-5l-engine/

You might take a look at this article.
On a fully warmed up engine at idle, the oil pressure, 5psi min. So says my database.
You might be able to use an analog gage in place of the oil pressure sending unit, to double check oil pressure.

It is located on rear of engine back by the distributor use to be. see attached pic

Having changed the oil sending unit it is a fair bet the oil light is operating accurately unless there is a wiring problem in addition.

Presumably you are referring to the oil pressure warning light rather than a light warning of a low oil level or high oil temperature? If you are in doubt I suggest you read your vehicle handbook.

An engine should not be operated with low oil pressure and it is risking some very expensive repairs and a lot of inconvenience if the cause is not located and rectified as soon as possible.

A common cause of low oil pressure is the engine could be dirty inside due to infrequent oil changes or poor quality oil. Another possibility is an oil pan or sump that is dented due to grounding. The suction pipe is only about a quarter-inch above the bottom of the oil pan and a relatively small dent can prevent a sufficient supply of oil reaching the oil pump.

I hope this helps.

thje po420 need to monitor o2 sensors to verify if you have a bad sensor or bad catalitic converter
the po522 oil presure sending unit

That is easy just above the oil filter just below the ac unit. Near impossible to get to. Remove tire remove splash shield and there it is but there is no way to disconnect the wiring right. If you don't care just pull the wire off and unscrew it. I didn't want to break the locking tab so I took it in and they said wait for it and they would charge me 75 dollars six hours later they finished and charged me 75 dollars. Have someone else do it

The change oil light tells you when to change oiul,If after an oilchange the light did not go out it must be reset.
Location oil pressure sending unit 2004 stratus Google Search

You have two problems going on.
The oil light is telling you the engine oil pressure is low. If the oil level is full, the sending unit for the light is faulty, or you actually do have low oil pressure.
The codes are for a leak in the EVAP system which could be the gas cap but could also be a number of other things. There are valves and hoses that could leak.
The engine oil pressure would need to be checked with a mechanical gauge, and the gas tank venting system would need to be tested for leaks.

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Right above the oil filter

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Regards, Lee Davidian

Might mean that you are nearly out of oil. Add necessary oil as to vehicle's specifications and the icon should go away. Oil change every 3,000 miles. Also check on the internet in Chrysler Pacifica oil problems just for your info. townhall-talk.edmunds.com/direct/view/???.f12caf4 - Cached If icon re-appears, have you vehicle checked by a certified mechanic as you may have other issues. (sensor, PCV valve, etc.). Hope this solves your problem.

just above the a/c compressor pully and to the left