Burl- With my experience with GMs, some check engine lights were not serious such as the loose gas cap. I've tightened down the gas cap and on the next fill up it goes out. I've never had a parts store check the OBDII but that is a possibility. I plan to get a Scan GaugeII which hooks up to the OBDII connector and reads the engine computer codes plus fuel mileage, tranny and engine temps etc. On running with the light on, I had a '82 Malibu that had the light on most of the time for years. When the light was out it would run rough. I think the newer lights / diagnostics are better. I have put over 300K on other GMs without a serious light.