Continuation of my last post from http://www.mynissanleaf.com/viewtopic.php?p=495975#p495975 ...
I've not had a single DTC P3131 nor yellow ! car light since the last one on 6/20/17.
Prior to 6/20/17, I had it bunch of times. I'd confirm it was the same code, clear it and the DTC and warning light would surface later within a day or maybe a week at most. As I think I mentioned elsewhere, a well-known Leaf tech in the PNW on FB suggested it might be due to a connected OBD2 dongle at the time of shutdown. I found 0 correlation to that. I could receive it when none was connected.
Anyway, from hints elsewhere here, someone turned off/declined data transmission to Nissan. I do that now and leave it that way. From my notes, it looks like that still doesn't help. And, oddly (?), even though it's declined, I will still sometimes (usually) receive charging complete/stopped emails from Nissan Connect. And, I can usually still check charging status and GOM via their iOS app.
I did do Delete Saved Locations & Reset Messages so my Saved locations for unplugged messages is empty. I think I turned off Autosave New Charging Station. It's hard for me to know what's really off/on because most Carwings settings are inaccessible when you decline and only accessible when you accept. It's unknown if the latter changes any settings/defaults.
I now definitely receive no more plug-in reminders.
I think the bolded part is the key to no DTCs. If possible, disable anything and everything related to transmitting, autosaving, and auto-updating. I haven't done any fuse or battery pulls since my last post on 5/31/17 nor called Nissan. Leaving my OBD2 dongle connected on shutdown hasn't caused any DTCs or warning lights either.
I usually park at work in a covered concrete parking structure (so no GPS signal) and sometimes in areas w/almost no AT&T coverage. Most of my charging is at work in that structure, as well. Sometimes, I move my car to/from the station within the garage, all w/o GPS signal. Sometimes, I charge underground in another garage (GPS cannot work down there).
Perhaps there's some bug related to added/preferred charging station locations and it wanting to send or not send a reminder? I wonder if my GPS and AT&T conditions on conjunction are related? I really hope Nissan can figure this out and issue a fix for this. Hoping the TCU is flashable.
MalcolmReynolds: As I said, I haven't mucked w/fuse nor battery pulls. If I had a dead 12 volt since the TCU upgrade, it's happened either only 0 or 1 time. I do at least weekly charge my 12 volt with an Optimate 4 charger, so if the TCU is causing an excess drain, my 12 volt charging is masking it.
I'd suggest you hold off for now, unless you really want to use the features. I do agree w/Gerry's point in finding a dealer that has plenty of experience doing the upgrade. I figured the one I went to would but I had to go back (http://www.mynissanleaf.com/viewtopic.php?p=492766#p492766). Don't worry about the "hack" reference. I'm pretty sure they were referring to https://www.slashgear.com/nissan-shuts-down-nissanconnect-ev-app-due-to-hacking-exploit-25429095/, which finally got addressed.