1.4l Oil Pressure warning on startup

Just put a new Transmisson and turbo on my friends 2012 Chevy Cruze, after getting it back together it shows the oil pressure warning display on start up and lasts for about 30 seconds before disappearing, it only does it on startup, I did an oil change in hopes of it fixing the issue with no luck. Car has no rattles or odd noises,

Running 5w30 full syn dexos rated 4.25qts and oil is showing on the dipstick just fine

The motor runs like a well oiled machine so to speak, no odd leaks especially from the turbo feed and drain lines, it also does not seem to consume any crazy amounts of oil

The car has 80,000 miles on it and is a slavage title from getting T-boned back in 2012 when it was almost brand new so warranty is out of the question

When I put the Transmisson and turbo in I pulled everything out the top. Everything seems to be plugged in tightly but I could be wrong

The car has the common PCV valve issue but at the moment I am trying to get it back to being drivable then I'll handle that issue, also it has a dead MAP sensor and is throwing various Map and turbo pressure codes, again this will get handled but I want to fix the oil pressure light first.

Has anyone run into this? Also can someone tell me the exact location of the oil pressure sensor, I wasn't looking for it when the motor was out haha