check engine light over 55 mph?

I have a 95 Skylark which runs fine. My problem is whenever I drive over 55 mph or thereabouts, the check engine light comes on and stays on for as long as the car in running afterwards. The car seems to run fine although the light is on. The strange thing is that the light will come on only when driving at those speeds. Around town, the light never comes on.

Any ideas?

On my 96 w/a 2.4l the Check engine light and abs lights would come on at about 70 and stay on until I shut the car off and restarted it. I also would like to know why.

I drive a 95 Skylark and my 'check engine light' comes on almost whenever I drive it. I nearly always drive at higher speeds because I live near a highway but the two seem related. I actually find the light goes on when I've been driving a high speed and then slow down. It will light up whether I brake or just take my foot off the gas.