SCI is "Serial Communications Interface". During communication, there is data there and a voltmeter tells you nothing.
Other times, the static voltage can tell you something about module health.

Read this:
https://www.autonerdz.com/yabbfiles/...etwork_ppt.pdf


Now, would you like to stop there or would you like me to tell you why you are wasting your time? (Not being snotty, I can tell that you are headed down a blind path...........)