To start off i will say that my cavalier always started hard but it always started. one day my wife tried to start the car and it would only crank.
things I hav already checked;

plugs, wires, coil packs. all have great spark
changed the ignition switch
new battery
checked voltage to the fuse box under hood
ign fuse 50 amp 12 volts
battery 1 40 amp 10 volts
battery 2 40 amp fuse 10 volts
abs 50 amp 0 volts
cooling fan 30 amp 0 volts

pcm 10a 10 volts
in car fuse box
pcm/ign 10a 1o volts

all checked with key forward in on position
car will crank start and immediately die. key is worn and tumbler turns rough. an after market radio was installed before i got the vehicle. i cannot pull a cel because my obd2 censor will not boot up or register the car. any help would be awesome thank you.