The ignition/steering wheel switch also activates the anti-theft system
The ignition/steering wheel lock starts the engine and, with the ignition key removed, the anti-theft system (PATS) for a few seconds. As a result of a half-turn of the steering wheel without the ignition key, the steering wheel lock enters the groove of the lock.
In my experience, the mechanics of the lock rarely break down. In older cars, it sometimes happened that the ignition switch contacts were stuck together or rusted. Unfortunately, the board with contacts cannot be replaced separately; the entire steering wheel/ignition lock must be replaced - this work is best left to a workshop. To check the anti-theft system, you should always look at the control lamp above the clock before leaving the car. The anti-theft system is ready for operation only when the lamp flashes approximately every 2 seconds with the ignition off. If your Focus has difficulty starting the engine, pay attention to whether the lamp goes out after about 3 seconds, or instead switches to a fast flashing mode for one minute, or is constantly on. In this case, the system did not recognize the key coding. Then remove the ignition key and restart the engine after 20 seconds.
Important for data flow - do not shield the ignition key with metal
If the indicator light stays on continuously for one minute and then flashes irregularly several times, the system has detected a malfunction. First, check that the ignition key is not shielded by other keys or metal parts (keychain). If this is not the source of the defect, get a spare key or recode the silent copy with the original key. If this seems too laborious, your Ford dealer can also help you.