Most late model cars and light trucks use a Start button instead of an ignition key to start the engine. The Start button must receive a coded signal from a Smart Key fob before it will start the engine when you press the button. If nothing happens, it may mean one of several things:
The battery inside your key fob is dead or too low to send a good signal to the keyless entry system and needs to be replaced.
The key fob itself is defective. This will require replacing the fob with a new one, either from a car dealer or an aftermarket fob (which will have to be reprogrammed to your vehicle by a car dealer or certified locksmith).
You are not pressing down on the brake pedal, or the brake pedal position switch is defective, or the transmission gear selector is not in Park. On vehicles with manual transmissions, you have to fully depress the clutch pedal before the engine will start.
There is a problem with the keyless entry system or Start button. The keyless entry system may not be reading the signal from the key fob because of an antenna or wiring fault, or the Start button may not be generating a signal when you press it down. These conditions will require further diagnosis and will likely require having your vehicle towed to a service facility or car dealer for repairs.
Your car battery is extremely low or dead. This may require a jump start before your engine will crank and start.
If nothing happens when you press the Start button (and you are depressing the brake pedal or clutch pedal, and the transmission is in Park), or you see an error message on the dash that says Key Not Recognized or No Key Signal or Incorrect Key, the engine will not start until it receives a good signal from the key fob.
On some vehicles, all you have to do is press the dead key fob against the start button to start your engine. When the key fob is held in close proximity to the Start button, the system will read the keyfob whether the battery is low, dead or missing altogether.
On other vehicles, there may be a special receptacle under or near the Start button, or on the steering column, or somewhere on the center console (sometimes inside the storage compartment or even under the cup holder) for the key fob. When your key fob is inserted into the receptacle, the system will read it whether the battery is low, dead or missing. You can then press the Start button while holding the brake pedal with your foot to start your engine.
If you have a functional key fob that only needs a new battery, the engine should start after using this special procedure. If it still won't start, however, you have a problem with the key fob itself or the keyless entry system that reads the key fob.
If you have a spare key fob and there are no problems with the keyless entry system or Start button, you should be able to use the spare key fob to start your car. If the spare key fob does not start the engine, the problem isn't a dead key fob battery or defective fob. The problem is in the keyless entry system, Start button circuitry or possibly the engine computer.
Your vehicle will have to be towed to a service facility or new car dealer for further diagnosis and repair.
If your engine cranks but won't start when you press the Start button, the problem is not your key fob, Start button or keyless entry system. There is another fault that is preventing your engine from starting. Possible causes include:
An anti-theft system fault. This may require reprogramming at your car dealer.
A bad fuel pump, fuel pump relay, or no gas in your fuel tank (check the fuel gauge reading!)
An ignition system fault
A bad crankshaft position sensor.