Using Voltmeter

WARNING: This page is about a different car, the 2004 Hyundai XG350. However, it is still accessible from the selected car via links, so may be relevant.

Disconnect the APS connector.
Check the continuity between terminal 4 and sensor ground.

Fig 1: Idle Switch Voltage/Continuity Table
Courtesy of HYUNDAI MOTOR CO.
If out of specification, replace the throttle position sensor.

Fig 2: Checking Idle Switch Continuity
Courtesy of HYUNDAI MOTOR CO.