XC60 "stop/start service required"
 

I have the above message and a DTC of CEM-B11D914 Battery failure, but both batteries are fine. The S/S function does not work, and my version of the wirring diagram shows a Red wire going to the CEM from the Primary fuse box. This wire has 12.6v on it the same voltage as the small additional battery anyone had similar problem??

It's likely that the support battery voltage drops when under load (ie during stop/start) but looks OK otherwise.

I thought that may be the cause but since it never goes into S/Start, as far as I can see the battery is just sat there doing nothing. It never runs down? The CEM thinks its too low and never allows a S/Start.