[zhouqi]

I have my "engine service soon" light on for several weeks. and the code is P1404. I didn't find any carbon on the valve. And I also found that the "engine service soon" light won't come back if I only drive on local road after I setting off the code. However, If i drove on highway, the sound of engine was different at high speed(70 MPH) and the engine service light will be on again after a while.

someone told me that EGR valve will start working only the speed is higher than 40mph. so i figure that the difference between local drive and highway drive comes from the EGR problem,right? Do i need to change a new one?