2001 Prius Won't Start

I attempted to search for similar issues before posting again for the sake of find the answer then ask for help. I currently have a 2001 Prius with over 250,000 miles.

Engine attempts to start first second and immediately stops when turning key over.

Key is inserted and symptoms:
Dash gas gauge is "dancing" up and down in box levels constantly
Current gear is not visible on dash (Shows P D N but none are highlighted) although I know which it is based on position of shifter
No errors appear on the dash or LCD screen / Not a single check engine messages or nothing
Techstream does not get signal when trying to run a scan - Works on my functional 2003 prius

Potential issue: Coolant pump was replaced before from previous owner from a junk yard and was able to run fine - Had hybrid battery jerry rigged and was a mess since kept winging it with battery cell swaps and using a bluetooth app to erase error messages while driving everyday every minute but he made it through until could not start anymore. Prior owner attempted to fiddle with fuel pump wiring under the rear seat. He thought perhaps fuel pump was bad or not working. I attempted to connect it back together since it uses a electrical plug connection and he sold it unplugged.

Checked blue 15A fuse for AM2 as many other similar threads and symptoms indicate but fuse is not blown and working - I happen to have another 2003 prius that starts and swapped the fuse from there and same symptoms.

I attempted swapping the hybrid ECU and engine ECU from working 2003 and same symptoms. No start. Engine just spins for a second and stops

Using a good hybrid battery from working 2003 and a new 12V. Any where else I can look would help otherwise going to just sell on marketplace for parts as is. Guessing communication in electrical is cut short somewhere

 

At last I found the solution for this thanks to another forum post recently and connecting the two together to resolve the issue.
O2 sensor wire was cut and left dangling. This would almost instantly cause a short when attempting to start the car and the 4 wire leads make direct contact with each other. This in turn would lead to the shorting of the fuse "EFI 15A - Blue". What does EFI control? Looking online, we quickly see it controls

"Multiport fuel injection system/sequential multiport fuel injection system"

This makes sense as the bouncing fuel gauge would relate to this issue due to fuel not activating and thus engine start ups being blank after 1 second.

Removed the O2 sensor, replaced the 15A blue fuse, and car starts again. Hopefully this helps anyone especially with all the recent CAT thefts happening on our precious 1NZ-FXE engines exhuasts.