My wife's car was throwing the code P0015 out right after her trip to the state inspection.

We originally thought it was those inspection guys who broke the car, but after searching online, I don't think the inspection has to meddle with the camshaft by anyways. I did hear an inharmoniously loud noise when driving her car at a low rev about 2k RPM recently, but the acceleration was pretty slow though. It only happens at low rev and some certain occasions like speeding up from still, and back to normal once the speed reaches ~40 MPH.

Any advice and comment is appreciated.