Ok here's some background info: 2002 lancer oz 5spd, car has had the service engine soo. Light on for a few months but it ran fine so I nevear bothered to look into it. I wanted to reset the ecu to see if the service engine soon light would go away. So I disconnected the negative battery terminal for a couple mins. Connected it back and when I went to start it it wukdnt start.all accessories work in the acc. Windows radio etc. When I attempt to start the car everything shuts off, the gauge cluster lights come back on very slowly and there's a clicking noise coming from somewhere in the engine bay. Further when I turn the headlights on the front Ecu clicks. When trying to start it it doesn't turn at all, everything just dies, and the radio windows lights etc. Act as if the battery was draines....but then if I turn the key off and on again everything's back to normal until I attempt to start it again. Im at a loss if anyone's has any input pls let me know, I'm stumpedstumped

 

That sounds like the battery has enough juice to turn on accessories, but not enough to turn the starter. Try a jump or check your connections since you recently had the cable loose (tighten it up snug)
Tis the season for batteries to die. I've lost all four of mine this fall.