My 2001 saturn ls300 is making a slight thumping noise, almost like a flat tire. None of my engine lights on the dash are warning a problem. What could this be. I did check there is not flat and the tires have been filled properly.

How about a slipped belt on a tyre. WHAT? you say. The steel belts in modern tyres can slip and cause the tyre to have an out of line area. You can often see the problem if you have someone drive very slowly away from you while you watch the tread for a couple of rotations. If bad you will see it wiggle. If those are original tyres, it is likely past time for a couple of new ones.

Remember to have equally worn tyres matched (both left and right) on the front and the back two also matched to each other. Also, although it sounds wrong, the best tyres should go on the BACK not the front. The other way around can cause dangerous handling problems in an emergency.

Ok i will try your suggestion of observing the tread. They are not original, had them about 2 years now. Thanks.

Two years? How does the wear look? Irregular wear can create this type of road noise.

it does seem irregular, but is there any thing else beside tire wear that could be going on?

There is, but start with the tires. And if the wear is irregular you may want to have the chassis looked at. Irregular wear is often poor initial balance, significant wear, or poor tires, but there are other possible causes such as worn suspension components, tired struts, and overdue alignment.

Make a note about which end of the vehicle it seems to be coming from. Then rotate your tires. If the thunping moves, then it’s likely the tires and wheels. If not, then it’s something else.