Service Engine Soon Light

I have a 2001 LeSabre with 43K and the Service Engine Soon Light came on. I have only had the car for a week and I am not sure what this light or what system needs attention. :confused:

The check engine light comes on when the onboard computer diagnostics has found a fault in one of its controlling sensors. If it stays on, its needs attention. To get the specific fault code, for the circuit having the problem, a scanner tool is needed. If you have an Autozone nearby, they will do that for free. You then need to find a listing of the codes (a web search for "GM fault codes" or they are listed in a Hayes Manaual) for what they mean.