If your vehicle is showing security or immobilizer light stays on or flashes on the dash, here are the most likely causes and the parts you'll need to fix each one.
The transponder chip inside the key or fob is not sending a strong enough signal to the vehicle's immobilizer system, causing it to reject the key.
A weak 12V battery or poor terminal connection can cause the immobilizer module to experience a voltage drop, leading to communication failure during startup.
An improperly installed aftermarket alarm or remote starter bypass module can conflict with the factory immobilizer, triggering the security system.
The antenna ring located around the ignition lock cylinder that reads the key's RFID chip has failed, preventing the vehicle from recognizing the key.
Internal wear in the ignition switch or lock cylinder can prevent the system from properly reading the key or sending the correct power signals to the security modules.
The main computers responsible for verifying the key and allowing the engine to start have failed, lost their programming, or have a wiring fault.