MAP Sensor Issues

[JD3020]

Ever since i got the scanguage for my truck i've noticed my MAP sensor has never read good. In the summer it would read up to -1.3psi, or 13.4 absolute. As its gotten colder out it has gotten closer to reading 14.7, but the closest its been is -0.1. These are KOEO, and at idle. Running around it seems to read lower than my boost gauge as well. This summer i swapped in a sensor from a friends truck that read and acted exactly the same as mine.

So last week i ordered a new one off Ebay from bestpartshouse, and got it today. Its a Ford part, all grey(the new updated style), part # is F4TZ 9F479 A. Came in a Ford box, and looks brand new. Just unhooked my old sensor and plugged in the new one, and hopped in the truck. Old sensor is reading about -0.3 today, new sensor is reading -0.5. I haven't driven with the new sensor yet to see if it runs any different either.

So do i have 2 faulty MAP sensors, is there a wiring issue, or is there another issue somewhere? Pretty sure these trucks have Baro sensors, but thats not something i can read on my scanguage. I can get access to a Snap On scanner though if needed. But could that be causing this issue as well?


BTW, i'm not that far above sea level, so it should be reading pretty close to 14.7 which is why i'm trying to fix it.

 

[JD3020]

Just took it out for a drive. The trans seems to shift a lot cleaner now, which is nice. Also it used to have very peaky power delivery, like huge lag then it'd take off. A lot smoother now, and seems to pull a little bit harder. Overall for $100 i'm very happy.

So now i'm just confused as to why its reading .5psi low at idle.

 

[JD3020]

Anybody have an idea? Sitting around 14.1psi right now, while EBP is reading 15.