PO720, for our cars is a "CAN bus circuit". The assembly ala_xfire is referring you to ,is a serviceable item that is know to cause symptoms such as yours. Are your break lights working? Have you downloaded the free service manual? Section 21will help you follow along with the suggestions that are made. If your on a phone, scroll to the bottom of the page an hit " view full site". Click on ala_xfires signature to download the manual.