I went over to jump-start my neighbors Cavalier
when he couldn't get it to turn over.
Once we concluded it wasn't a dead battery, he called the dealer.
A tech came over, pulled a circuit board,
then clipped and spliced a wire. ... Car started !
Tech sez; "the anti-theft board that checks the key
often fails without warning."
Unless the owner wants the feature, it's easier
( and cheaper ) to disable and remove.
First thought; If the tech could disable the circuit in a few minutes,
does the "key chip" really have an anti-theft value ?
Second thought; At one time, you had
the key switch, and the starter solenoid.
Now, there's the keyswitch, the anti-theft circuit,
the "car in Park" switch, and, God knows what else.
It's not a fix-it-yourself" thing any more.