Why can't the car key unlock the door?

[CharlieLee]

There are several reasons why a car key may not unlock the door: 1. The remote key battery is dead or the car battery is depleted; 2. There is strong signal interference in the vicinity - in this case, you can use the hidden mechanical key inside the remote key to open the door; 3. If even the mechanical key fails to unlock the door, it may indicate that the car's central locking system is in an electronically locked state. You'll need to wait one or two hours for the lock to disengage before attempting to unlock again. A remote key refers to a system that allows doors to be locked or unlocked from a distance without inserting the key into the lock. It works by emitting weak radio waves from the owner's vicinity, which are received by the car's antenna. The electronic control unit (ECU) then identifies the signal code, and the system's actuator (either a motor or electromagnetic coil) executes the locking or unlocking action. This system mainly consists of two components: a transmitter and a receiver.