Car Dies at a stop


Thought I'd post in other forums because I only got a few relies in the W212 forum. I have a stock 2014 E63s with about 60K miles on the clock. I've had random but continuing issues where the car dies at a stop. I have SDConnect with Xentry, and have pulled codes several times. The only thing the pops up is a B1F8D14, "The lower sensor of the rear switching module has a malfunction. There is a short circuit to ground or an open
circuit."
In an attempt to isolate, via Vediamo, the ECO Stop/Start function was permanently shut off because it first seemed as if the dying only happened when in ECO mode. Problem still exists. I know there is a "Relay Starter-Alternator Backup Battery" (A0009822023) that may be involved. A Google search of the code points to this site: Autologic Live: Electrical fault malfunction on Mercedes C-Class - autotechnician - servicing the independent workshop. Not sure it relates.
Any ideas of what might be causing this? Also anyone know what the "lower sensor of the rear switching module" is? Seems odd that the car doesn't throw a code when the car dies unexpectedly.
Thanks,
Joe


