Oil Pressure Switch

Check the continuity between the terminal and the body with an ohmmeter. If there is no continuity, replace the oil pressure switch.

Fig 1: Checking Continuity Between Terminal And Body With Ohmmeter
Courtesy of KIA MOTORS AMERICA, INC.
Check the continuity between the terminal and the body when the fine wire is pushed. If there is continuity even when the fine wire is pushed, replace the switch.

Fig 2: Checking Continuity Between Terminal And Body When Fine Wire Is Pushed
Courtesy of KIA MOTORS AMERICA, INC.
If there is no continuity when a 49.0kpa (0.5kg/cm² , 7.1psi) vacuum is applied through the oil hole, the switch is operating properly.
Check for air leakage. If air leaks, the diaphragm is broken. Replace it.