Hi and thank you for you r help. Im working on a 97 Chrysler Cirrus 2.5L engine with no communication with TCM, BCM, AND ABS, transmission sometimes works good other times slips and falls in limp in mode. I can't scan trans codes because of no comm. problem. I din't think it was a bad TCM, but i change it ans still no communication, then i change BCM and still no communication. With key on or engine running i have 2.5v. on BUS circuit at DLC, and TCM. What test can I do next to figure this out? How dous BUS REALLY work? Help. I have disconected cluster, tcm, ABS modules one at a time to see of one of them is the problem but no luck.