noise when 2000rm
 

I have a 01 S80T6,with 20000miles. I like it very much as it gives me confidence to drive smoothly but excitingly.

However, there is always a erro message of Emission system service required with Check engine light. I did not pay a lot attention to it as I was told that it's not a critical problem.

The problem lasts for around 1 year and now, I hear a certain of noise when engine speed reachs 2000rm. i found this problem just right after the regular checking service of 20000miles. The nosie seems come from engine but it is not, because there is no this noise when I am kicking the accelerator pedal with shiftof N. The noise only happens when running on the road.

The noise sounds like a kind of sympathetic vibration, or a noise from a valve. it only happend when engine speed is around 1800rm-2200rm.

I have no any idea about the potential problem. could any expert can help me to give me advice?

Thanks in advance

RE: noise when 2000rm
 

That means there is codes in the engine computer.