Kia Sorento 2001 General Information Manual page 1220

The transponder(inserted in the Key) has two stable positions(position 1 and position2 on the above figure).
Reading the transponder in these conditions should be possible at 100% rate:
• in the temperature range
• in case if extreme values intervening in the coupling between transponder and coil, which are:
→ carrier frequency
→ tuning frequency of the antenna resonant circuit
→ tuning frequency of the transponder coil
→ minimum magnetic field of transponder good operation
→ mechanical tolerances of positioning(transponder in the key and coil on the SCL)
• When the system is submitted to an electromagnetic field
Functional description
The trading transponder procedure is initiated by a rising edge in the Ignition input.
The transponder reading should be completed during a delay of 200ms after + ignition rising edge. This time includes two
possible tentative of transponder reading.
During this delay, all other requests are ignored.
Four transponders in total can be programmed in the EEPROM.
The ICU is unlocked if the transponder code read is know and belongs to the list in the EEPROM and if the transponder
has been authenticated successfully. ICU switches to the locked state after approximately one second after the + ignition
falling edge (Passive arming).The ICU is locked if the transponder is absent or the code read is unknown.