What does it mean when the "Service Engine Soon" light stays on while driving in a 1997 Chevrolet Astro?

Hi Ken...this could mean a few things but primarily it is a pre-program function installed by GM to get you to take your vehicle in for some basic servicing such as oil change and tune-ups...it all depends on the mileage of the vehicle...I had a 96 Astro with the 4.3 Lt engine and at about 90k miles the service engine light came on indicating it was time to change my timing belt, as well as some basic tune up stuff.....if your van is running good and you don't hear, feel or see anything strange going on, then you can turn off the "service engine soon" indicator by going to the GM website and searching for that help feature in their pull down menu...

The Astro has a timing chain, and no timing belt needs to be changed. This light is not a service reminder, it comes on due to a malfunction somewhere, which is usually the case, so you need to use a code reader in the OBD II plug, to find out what the trouble code is and where to start looking for the problem. Your advice is not correct.

Sometimes if my gas cap is loose it comes on