This started when my new used 2017 Fusion Energi stopped talking to the MyFordMobile app. After reading what a pain it was to pull the appropriate fuses to reset the 3G modem (?), I read that you could also disconnect the negative terminal on the 12V battery and let it sit for 10 minutes. Good news is that it worked and the MFM app updated immediately. Bad news is that when I went to reconnect the negative terminal, I got sparks when I put the terminal back on. VERY confused as to why, and I obviously don't want that to happen again. What did I do wrong and how can I avoid that in the future? (I'm sure the MFM connection will need to be reset again as I park in a parking garage and bad cell service is apparently related to the problem.) Thanks for the help.