Currently tracing a "no start" problem on the 05 roadster and have had the RCM repaired, so ruled it out.
While reading the service manual, it would seem that each module (or group of modules) has a pin on the Data Link Connector to module "SCI transmit" pin.
I have not found the definition of SCI transmit, but am thinking this is a diagnostic indicator of health for the module.
If I am correct, then it would be beneficial to have a list of measured values recorded in this tread, with key in the "on" position, engine off.
This way a baseline could be established for faster determining where a potential problem could be located.
Would it be possible for one or more contributors to this forum to measure and record here those values?
Thank you

 

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...........)