The knock sensor is a complete pain in the tailgate to replace. You have to remove the air plenum, the intake manifold, the timing belt and lots of other stuff to get at it.

Q: My 2000 Nissan Pathfinder was diagnosed with a knock sensor problem after a mechanic scanned the OBD2 codes. (The check engine light is on.) It did not pass the annual inspection. The car has ...

They all have knock sensors that automatically adjust the timing if you happen to get gasoline that has too low of an octane rating. So it's possible you have a bad knock sensor.

In response to these reports of malfunctioning engines dating back to 2010, Hyundai-Kia has developed a software update they call a knock sensor detection system.