Trunk Lid Open Switch

Remove the trunk trim.
(Refer to TRUNK TRIM REPLACEMENT .)
Check for continuity between the Trunk actuator terminals.

Fig 1: Identifying Trunk Actuator Terminals
Courtesy of KIA MOTORS AMERICA, INC.
If continuity is not specified, inspect the switch

Fig 2: Trunk Actuator Continuity Chart
Courtesy of KIA MOTORS AMERICA, INC.