Once started, a keyless car can typically drive indefinitely without its key until it runs out of fuel or the driver intentionally turns it off. The vehicle only needs the key (or fob) present to initiate the ignition process, not to continue running.
The Mechanics of Keyless Operation
Keyless ignition systems, often called "push-button start," work by detecting the presence of the key fob within a certain range of the vehicle. This allows the car's computer to authorize the engine to start. However, once the engine is running, the continuous presence of the key fob is generally not required for the car to keep operating.
- Starting: The key fob must be detected inside the vehicle for the engine to start.
- Driving: Once started, the car's engine does not typically monitor for the key fob's continuous presence to remain operational.
Most keyless vehicles will issue an audible warning and/or a dashboard message if the key fob is removed from the car while the engine is running. This is a safety feature to alert drivers who might accidentally leave the key behind (e.g., if a passenger exits with the key).
Driving Distance Without the Key
There is typically no limit on how far a keyless car can drive without its key once it has been started. Criminals often exploit this fact; they can steal a keyless car (e.g., via relay attack) and continue driving it until it runs out of fuel or they reach their destination.
What Happens If You Stop?
While the car will continue to drive, a critical point to remember is that if you turn the engine off, it will not restart without the key fob present.
- Example: If you drive to a gas station, turn off the engine, and realize you left the key at home, you will be stranded because the car will not restart.
The table below summarizes keyless car behavior without the key:
| Action | Key Fob Present (Normal Operation) | Key Fob Absent (After Starting) |
|---|---|---|
| Engine Start | Allowed | Not Allowed |
| Continuous Driving | Allowed | Allowed (indefinitely) |
| Restart After Engine Off | Allowed | Not Allowed |
| Dashboard Warning | No (unless fault) | Yes (audio/visual alert) |
Preventing Keyless Car Theft
Because keyless cars can be driven indefinitely once started without the key, they are a target for thieves. Many modern keyless car thefts involve sophisticated methods like "relay attacks," where criminals use devices to amplify the key fob's signal from inside a home to the car outside.
To protect your keyless vehicle, consider these preventative measures:
- Faraday Pouch/Box: Store your key fobs in a signal-blocking pouch or metal box, especially overnight. This prevents criminals from intercepting or amplifying the signal.
- Steering Wheel Lock: A visible physical deterrent like a steering wheel lock can discourage thieves.
- OBD Port Blocker: This device can prevent thieves from reprogramming a blank key fob through the car's On-Board Diagnostics (OBD) port.
- Parking Location: Park your car in a secure, well-lit area, ideally a locked garage.
- Software Updates: Ensure your vehicle's software is up to date, as manufacturers sometimes release security patches.
- Check for Recalls: Stay informed about any security-related recalls for your vehicle model.
For more detailed tips on preventing keyless car theft, you can consult resources like the American Automobile Association (AAA) on how to protect your keyless vehicle.
