Why does check engine light turn on when vehicle reaches 60 m.p.h. ?

I have a similar problem, except that mine comes on at or above 40 mph right away, while below 40 it takes a few minutes. Several mechanics have tried to figure it out with no luck, but they have all said there is no actual problem that would cause the indicator to come on. I think it is just another (minor) problem with the Accord's funky wiring