My check engine light has just come on. I have 48000 miles on my 2005 Trailblazer. I also have the engine whine. It goes up with engine RPM. I tried belt dressing and that quieted it a bit. I am not sure if the two items are related. Can anyone tell me what things can cause the check engine light to come on. I have tightened the gas cap as well. This is all I have done so far.