KIA Niro: Smart Key System / Description And Operation


The SMART KEY system is a system that allows the user to access and operate a vehicle in a very convenient way. To access the vehicle, no traditional key or remote control unit is needed.

The user carries a SMART KEY FOB which does not require any conscious actions by the user (e.g.

operate a RKE button). The SMART KEY system is triggered by pressing a push button in the door handle.

After being triggered the vehicle sends out a request in a limited range. If the SMART KEY FOB receives this request, it automatically sends a response to the vehicle. Then the system decides whether to perform a particular action (unlocking, locking...) or remain inactive.

Again, a communication between the vehicle and the SMART KEY FOB is needed before any actions will be performed.

The System offers the following features :

  • Passive unlock via 2 doors
  • Passive locking via 2 doors
  • Passive start
  • Passive access tailgate via the tailgate lid switch at the tailgate
  • Max. 2 fobs can be handled by the system
  • Immobilizer backup antenna driver integrated into SSB for TP authentication (i.e. limp home mode)
  • Communication with engine management system
  • LF-RF communication
  1. Passive unlock

The system allows the user to access (unlock) the vehicle without performing any actions with the SMART KEY FOB.

  1. Passive locking

The system allows the user to lock the vehicle by pushing a button on door handle with the SMART KEY FOB.

  1. Button start

The system allows the user to switch the power modes (Off, Accessory, Ignition), as well as to start and stop the vehicle's engine without performing any actions with the SMART KEY FOB. See Button Engine Start system specification.

  1. LIMP HOME Mode

Additionally, the system offers so called "limp home mode", which is the user can operate all vehicle functions by pushing the key into the SSB.

Smart Key ECU (SMK ECU)

The SMK ECU manages all functions related to "Passive Unlock", "Passive Lock" and "Passive Authorization for Engine Start Operation".

It reads the inputs (Push button in door handle, Start Stop Button (SSB), PARK position Switch), controls the outputs (e.g. exterior and interior antennas), and communicates via the CAN as well as asingle line interface to further devices of the car.

For communication with the SMART KEY FOB, SMK ECU generates a request (challenge) as an encoded and modulated 125kHz signal at the inductive antenna outputs and receives the SMART KEY FOB's response via the external RF receiver.

The main functional blocks of the SMK ECU are :

  • Power supply
  • Microcontroller with FLASH Memory
  • Single Line Interface to EMS
  • Input stage
  • LF antenna amplifier/driver

The LF antenna amplifier/driver generates a 125kHz sinusoidal carrier signal which is distributed to the different antennas.

Smart Key FOB

The system supports up to 2 SMART KEY FOBs.

The main functions of the SMART KEY FOB are :

  • Passive functionality: receives LF-challenge and sends automatically RF response.
  • Classic RKE function by action up to 3 or 4 buttons.
  • Transponder-functionality in case of a flat battery or a disturbed communication.


  1. Emitting LF Antennas :

Inductive antennas in and at the vehicle are used to transform the current, driven by the SMK ECU antenna driver, into a 125 (or 134.2) kHz magnetic field, which is the carrier for the SMART KEY challenge.

Three antennas cover the vehicle's exterior: two antennas in the Door Handles (DS and PS) cover the area around the doors; one antenna in the rear bumper covers the area around the tailgate or tailgate.

Up to three antennas cover the vehicle's interior and the tailgate or tailgate interior: two in the passenger compartment and one in the tailgate room or tailgate.

  1. Bidirectional Immobilizer Antenna (for Limp Home): The Immobilizer Backup Antenna is used for sending and receiving data: it emits a magnetic field (125 - 135 kHz challenge) and receives changes in the field strength (response of Transponder).
  2. Receiver

The SMART KEY FOB's response is received via the RF receiver.

Door Handle

The front door handles of the two doors (driver door / passenger door) are equipped with emitting LFantennas to emit the 125kHz signals. The front door handles are also equipped with a push button.

Push Button

The push button in door handle serves as a trigger to indicate the user's intent to unlock or lock the vehicle.

The push buttons are installed at front doors, integrated into the door handles.

Another button is installed at the tailgate or tailgate lid.


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