[Bank 1 / Sensor 1]

Switch "OFF" the ignition and disconnect the negative (-) battery terminal.
Disconnect the connector (A), and then remove the sensor (B).
Heated Oxygen Sensor:

39.2 - 49.1 N.m (4.0 - 5.0 kgf.m, 28.9 - 36.2 lb.ft)

Fig 1: Removing Heated Oxygen Sensor Connector
Courtesy of KIA MOTORS AMERICA, INC.

Fig 2: Removing Heated Oxygen Sensor
Courtesy of KIA MOTORS AMERICA, INC.