As the others say, there's no bus. The reason is that the S-bahn/train connections are too good, with departures every 20 minutes and a travel time to the Hauptbahnhof in Heilbronn of 1:25 hours, while going by car takes about 1 hour if there's no traffic jam at the A8/A81 intersection (Google maps claims it takes 50 minutes, but it doesn't take into account the work done on the A81 in the Stuttgart area, with speed limits of 80 km/h and rather frequent traffic jams).

So my suggestion would be to take public transportation and then take a taxi from Heilbronn Hbf to your final destination.