Chevrolet: Service Engline Soon light, 1995 chevy lumina, chevy lumina

Question
Hi! I have a 1995 Chevy Lumina Minivan.  The "service engine soon" light came on a few times, while driving on the highway.  As soon as or, each time I'd shut the ignition off and turn it back on again the light would be off and I won't see it on again for a while.  I already had it checked with the computer twice and could not find anything wrong with it.   I have not seen the light on for a week or so.  Is there really anything wrong with the minivan or just a sensor glitch?  Otherwise, it runs fine.

Answer
Hi Stella;
          I have the same thing going on with my 99 silverado , on than / off - it is telling you that soon there will be something that will need to be replaced ,    -when one of the computors sensors run a bit off the norm.from dirt or fouled up- it causes the light to come on,
 , but as long as it is running good , like my  truck it will be ok. when it (stays on) than you will have to have it checked .I bet it is a sensor. ok