98 beetle will either clear the code upon initial start up if its senses there is nothing wrong with the system. If not it can take up to 3 full drive cycyles ( operating temp.) If not the code will eventually clear but can take up to 75 full drive cycles. Easiest thing to do if it dosent reset it self automatically, go to auto zone and ask to use one of the obd2 scanners and clear it yourself, then run the codes to make shure it is clear. Auto zone personel will not clear the codes but im pretty shure if u slip them a 5 they would. Or just do it urself with their scanner. As far as the battery thing goes it works on some vech. but usually after u disconnect both cables you have to tap them together not on the battery of course, ive found that works too.