car

Check anti-theft. Sometimes the fobs can act janky when they, or the battery in them is replaced. If that all checks out, make sure the battery terminals are tight. If so, have your starter and alternator tested.

Help

Ok thanks but wat is a fob? I reset it according to owner manual when I turn key on everything works but when I turn ignition to start nothing

The fob is the remote you use to unlock/disable the anti-theft system on the car. Try resetting it again and arming/disarming the system a few times. Did you get it right from a GM dealer or aftermarket?

Almost sure it's a original it opens door.and locks them ok someone mentioned about a anti theft sensor?

Yes, the anti-theft will keep it from starting if the fob is not programmed correctly. Did you replace the key as well?