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Discussion Starter · #21 ·
No. Some users have reported error messages appearing (after 12V failure/replacement), & then mysteriously vanishing "after driving a few days/times". Others have noted that's due to 5 key cycles clearing codes for errors that have been corrected. Even if they're wrong, it's quick & easy to try, & hopefully then report back here whether it worked or not.
 

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Discussion Starter · #22 · (Edited)
Good News Update!

HV disconnect CAN work, when all else fails. Thanks to user "ratfinkharley" reporting on the other forum. 12V replacement gave error codes & prevented shifting to D, even after subsequent 12V disconnects & key cycles.

Here's the new sequence to try for these sorts of glitches:

First try the following THREE:
(try whichever is easiest for you first)

1) Alfa OBD code clear.

2) Key off 3 minutes. Repeat as needed, up to 10 times. (1 to 3 times off 1.5min is the most I've needed, others say 5-10 times, nhtsa says 3-5min for "sleep" mode).

3) Key off 5-min*, THEN disconnect 12V. 30 second disconnect worked for me, but when that & 30 minutes failed for someone else, 30 hours worked.


IF all those fail, the next thing to try is HV disconnect IN THIS SEQUENCE*:

1) With the car in "ready" mode, open the hood & left door, & don't open or close ANYTHING for the entire process (avoids "wake up" signal).

2) Remove the key, wait 3 minutes for "sleep" mode, & remove the orange HV plug under the rear seat bottom.

3) Disconnect the 12V, replace the HV plug, & reconnect the 12V.



*That is the sequence officially recommended by nhtsa.gov Most likely 3 minutes off is plenty for 12V disconnect, since it's sufficient for HV disconnect.

ratfinkharley just opened both doors & hatch, turned off the key, waited 5 min, unplugged/plugged the HV, then did a 2-min 12V disconnect, & it worked, even though it's not the recommended sequence.
 

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Hope this may be of help so some others. My 2016 500e with 12k miles suddenly greeted me with a "Limited Power Mode" display, the turtle, and the car w/exclamation point. With heart in throat, I scurried back to my garage (I had only gone about 80 yards), parked it, and pored through the owner's manual, then came here to the forum. After reading all the posts that mentioned LPM, I decided to try the easiest thing first: check my (original) 12V battery. Since I don't have an adequate piece of equipment to test it, but it SEEMED to be alright, I charged it the rest of that day, over night.... and into the next day. Still had the LPM and related messages. So, the next day I pulled the 12V battery out, took it to my friendly Interstate Battery shop, where they tested it, and said it was good...... hmmm. Spirits low, I called the nearest Fiat service department (38 miles away), got an appointment for 12 days out, and scheduled a tow truck to take me and my car to the service department. Then, the next day, I put the battery back in the car, buttoned it up, and opened the driver side door...... yup, the instrument display was just like it was before the LPM messages showed up! I have a couple of questions: why did I get the LPM message? why did it go away? was it an aberration? does the condition that generated it still exist? am I living on borrowed time with my 5 yr+ old battery? ANY thoughts or discussion are welcome, and thanks in advance!
 

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Discussion Starter · #24 · (Edited)
First, please relax, since your car is almost certainly fine. Mine is 3 years older than yours, with more than double the miles, & it's fine too, as are all the others reporting in with double or triple MY miles.

Like any other computer I've ever dealt with, this car gets little glitches once in a while*, requiring reboot. In this case that's usually done via a few key cycles or a 12V disconnect, which you did on accident. The above thread's HV disconnect is pretty much the last thing to try if nothing else works**. Please check the list here:

Many of the false alarms seem to be caused by the 100% unnecessary humidity sensor, including ABS, RBS, HSA, PRND, & SRS (airbag). I strongly advise deactivating it, as I did over 5 years ago, with excellent results:

 

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Discussion Starter · #25 ·
* I unplugged my humidity sensor about 5 years ago, so in that whole time, all but one of my own glitches were from user impatience, like flicking the key to "start" for only 1 microsecond, or shifting to D while moving (like coasting in N out of a parking spot). All were corrected by 1-to-3 key cycles, including the first cycle where I'm too impatient to wait for it to fully shut down, & even that 1st cycle often works.

The ONE glitch that wasn't my fault was an "infection" from the absolute oldest local public charger. It suddenly made ABS activate every time I braked below 6mph. I had not yet learned about 3-5 minutes key-off (for key cycle OR 12V disconnect) so I just pulled the negative 12V terminal for 30 seconds & then it was fine.

** After a few more users report success with HV disconnect, it may move up the list to try whenever you feel like it, since it's much quicker than almost an hour to do the ten 5-minute-off key cycles, let alone the 30-hour 12V disconnect.
 
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