How do you remove bad odor from a Saturn Ls?

It depends on the source of the bad odor. If the carpet is loaded with rotting "stuff", you'll need to either clean or replace the carpet. Same with the upholstry. On the other hand, if the AC has been run primarily in "recirculate" mode, you have built up mold in the evaporator coils. During normal operation of an air conditioner, condensate builds up and is supposed to flow out through the condensate drain. You can build up a lot of water through condensate, so you need to make sure the drain is working properly. Generally though, if water isn't dripping inside the car from the air handler box, the drain tube is probably ok. Even if the drain tube is functioning properly, the constantly damp evaporator coils can build up mold which will eventually stink. It's disgusting, and it's the same for all vehicles. You need to make sure you're getting outside air. Turn the AC controls from recirculate (or MAX) to normal. If the smell doesn't go away within a few days you may need to have it professionally cleaned.