the P0601 is 95% of the time a bad PCM, i would start by replacing it, you can find new ones on ebay which come pre-flashed (you give the company your information) and then you just plug it in and go, any codes that come up then are the ones i would look at.
the o2 sensor could be nothing (has it been really wet were you live?, maybe water got in the wire harness) and the IAC could be a loose connection, a bad wire or a bad IAC motor which is easy to replace.
live in NJ?
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