The icon of a green key in the instrument panel is normal although many of us never notice it. The green key will come on when you turn the ignition key to the start position. If everything is working correctly the key will blink once and go dark and the car starts. Where you insert the ignition key there is a component around the key hole called an Immobilizer. It is part of the anti-theft device in the vehicle. It’s job is to read the chip in your key fob ,,, if it’s the right information for that particular car, the Immobilizer will inform the car’s onboard computer and the vehicle will start. Every vehicle has its own unique code and is identified by the vehicle vin number. If the code is wrong or the reader is not functioning the computer will shut the fuel and firing systems down and the car will only turn over but will not start , some vehicles will crank up but then immediately shut off.