Hi my check engine light goes on for a couple days no sign of reduced engine performance, then goes out on its own. I checked the codes and got code P0401- EGR flow insufficient. Visually there is no sign of a problem at the EGR. The Tercel is in good shape about 87k miles and is used primarily for shopping trips maybe 35 to 50 mph operating speeds. Im guessing it may be some carbon blockage in one of the EGR passageways. If anyone as insight into this before I take here apart I would appreciate knowing more before I dig in.