so i changed my oil on my car which is a 2001 Z24, yesterday...everything went fine and then i go to start my car and it wont start....so today i looked at everything i could and found a sensor pulled out and i found where it went....right above the oil filter. so i put it back and still the car wont start..now im thinking the battery is dead so im gonna get a new one but is there something else thatcould be wrong??? lemme kno any ideas thanx

john

ya that sensor is the camshaft position sensor without it wont start..lol make sure you didnt rip a wire and make sure its all the way plugged in..

I was sure the Z24's cam sensor is up by the valvecover/coilpacks, at least it's that way on my brother's 98 Z24. I'm thinking it may be an oil pressure sensor that got pulled out, and my theory is that the PCM sees 0 psi of oil pressure it won't let the engine start.

That's correct. The one by the oil filter is the crankshaft position sensor. The one up by the IDI cover is the camshaft position sensor. Easily confusable when you're typing in a hurry. Check all your wiring before getting a new battery, might just be a loose connection.