po 1401

Hi guys, I got the engine light the other day, po 401 EGR flow insufficient. As every year or so I get it, not a big issue. Car runs smooth at idle. I went ahead and cleaned the egr, pipe tube and gave it a rather good induction service with seafoam and a IV drip. Cleaned the throttle body and blue out all the junk. Cleared and check the codes, and it came back, "PO 401" Went into data stream and it said the DPFE sensor was at 4.99 at idle. when its supposed to be at about 1.0 if I am not mistaken. So I ahead and changed the DPFE. Checked for codes and nothing. The next day right as I started the engine cold, the light came on. I scanned it and it came up PO 1401 WITH Emissions being the problem. As I looked on the internet, I found that it could be a defaulted DPFE sensor, or a bad PCM. Could a vacuum leak at the air box cause this? How do I check for a bad PCM and is a common thing with a 95 town car? I haven't heard of a PCM going bad, but would like some extra input.


Bryan
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