2000 Pontiac won't start

What kind of pontiac, engine type, tranny and miles on the vehicle. Does it have a key with a computer chip? Also are you getting spark? Do you have fuel pressure? Can you hear the fuel pump run when yu turn on the key? Let me know

Hummm. In that car the fuel pump relay comes on for 3-5 seconds and primes the system. The circuit then goes through the oil presure switch to the fuel pump. This prevents engine damage with no oil pressure.

There is a red wire with a green connection that is a fuel pump test wire. It is somewhere in the engine compartment and is easy to find. If you apply 12V to that wire and the car runs then the fuel pump is OK and the problem is somewhere in the relay to oil pressure sw to the tank. The fuel pmp wire is light gray from the oil pressure sw to the tank.

My best guess if the oil pressure sw. Good luck

It is usually near the oil filter. Good Luck

Did u find the red lead to test the fuel pump?

You need to see if you have fuel pressure and if the injectors are pulsing from the computer. Let me know

Nope, the O2 sensor monitors the amount of oxygen in the exhaust and control the air mixture. A remote possibility is a coolant temp sensor. It is near the T-stat and has two wires. I can't help only guess because I don't have enough info to analyze the problem even with 40+ years of experience.