While I was investigating the TPMS system fault in another thread, I learned that the SJB (Smart Junction Box) which houses the TPMS functionality apparently contains a battery that allows it to maintain its nonvolatile configuration data in the event the 12V system of the vehicle is depowered. A new SJB from Ford comes pre-set with a bunch of DTCs that have to be cleared. First the old data is uploaded to IDS, then the new unit is installed and reprogrammed with the old configuration data and the technician is supposed to clear the DTCs and train the TPMS system. Since the SJB is also intimately tied to the remote keyless entry system and the PATS system, as well as the *interior light dimming function* this step has to be performed correctly or you have a screwed-up PATS and maybe a car that no longer recognizes its keys?

I wonder: How many modules are there in the FEH that contain their own batteries to back up their nonvolatile memory? As these cars get older, it seems reasonable to expect that a lot of them will die of old age - particularly if the "owner" let the car sit for months or years without a good 12V battery in it. The modules will deplete their battery backups, lose their data and then then you'll get DTCs indicating bad modules, but really all that's wrong with them is the battery inside them?

Does anyone know how many there are and which ones? It might be a bit of a pain to open these units up and replace the batteries, etc., but wouldn't that be better than buying new or used units that also contain old batteries that are going to fail?

If we had a comprehensive list of them, someone could plausibly run a side business replacing the batteries, reprogramming the modules and then shipping them back to the customer.