I have a 2000 pontiac bonneville and it was running fine then all of a sudden I came out of a store and it wouldn't start. It started the first 3 times I tried, but it ran really rough like it was only running a few cylinders then it just won't turn over at all. The "check gauges" "service engine soon" and the only code I'm getting is a "low tire pressure" code. (All 4 of the tires are at 50 psi) - I like them at 50 when drive far. The car was running 100% after I put a new Fuel pump and gas tank and battery in. I made a 3800 miles trip across the US and all was fine the whole way. Now I'm stuck across the country with a car that won't even start. Any help will be great. Thanks in advance.

Welcome to the forums!
Could it have been bad gas added? Try a fuel stabilizer/water remover..
Did you have a tune up done new plugs/wires, or ever replace the fuel filter?
I would check a few plugs to start with check gap & condition, replace as necessary.
Probably best to get a fuel pressure reading as well, also try a shop scanner to see if there are any other codes present.