Vibration felt in cabin when A/C compressor engaged.
Issue appears to have been caused by engine cooling fan. Fan removed - bearings in track of fan casuing "out of balance" condition when fan spinning at high rpm. Fan replaced under warranty
Throttle position sensor was bad and the car was in "limp mode" and had to be towed into the dealership.
Persistent engine check light on. Brake sticking.
Timing belt replaced under warranty
Throttle position sensor going bad. Technician replaced the wrong sensor and misdiagnosed problem even though it is a common and widespread problem with Hyundai. Replaced throttle position sensor.