Vehicle Anti-Theft System (VATS) is a security system that utilizes an electrical code (a resistor pellet) embedded in the ignition key. VATS key is just an ordinary flat metal car key that has an electrical resistor embedded on the shaft of the key.
The VATS module in the car reads the value of the resistive chip embedded in the ignition key. When the VATS module sees the correct value on the key resistor, it allows the starter and fuel pump to work. If the VATS module doesn’t see the correct value, it shuts down those components so the car will not start.