Hello, I have a 2005 3.4L Chevy Venture van with 215k mi on it. Recently the fuel level gauge became erratic and the check engine light also came on at the same time.The codes stored were Po453 evap. Emission system pressure high and also Po463 fuel level sensor A circuit high. I noticed while looking at a wiring diagram that the evap code is for the fuel tank pressure switch which also shares a ground with the fuel level sending unit. Just wondering if this is an electrical issue or if something else is going on.Any advice on where to start looking at this would be appreciated.

Really this means: Evaporative Emission System Pressure Sensor/Switch High <<<<<----This "switch high" is important here, it could have this from normal pressure and bad electrical
So . . . four highly-reliable systems failing all at the same time, or . . .

. . . bad ground supporting all of them. I think you are on the right track.

Probably something corroded under there.

Thanks so much Cathedral Cub for the quick reply and encouraging me to go the corrosion route. I ended up getting under the vehicle tonight and pulled the 8 pin fuel pump connector harness that goes into the underbody and found it was filled with water. I emptied it out and cleaned the pins as best I could and all seems fine now.
Thanks again for your support.

Great news!

Thanks for letting us know how it turned out!