2018 F150 5.0
Yesterday my “service engine soon” light appeared and explanation was a miss fire was detected. I unhooked the negative cable for a few minutes to reset the light. Today when I attempted to start the truck the battery was dead. I am currently charging it now and plan to have the battery checked. Anyone ever have an experience like this? I have no idea what could have caused the battery to drain with cable disconnected. Any thoughts?

 

Update:
Battery fully charged. Still won’t do anything. No power at all. Any suggestions?

 

Latest Update:
Had my battery checked and is 100% ok
Re-installed the battery and it started right up all electric good. However, the “service engine soon” symbol is still illuminated? App says a miss-fire was detected…Any thoughts?

 

obviously you got a misfire ..

 

Yes, obviously a mis fire occurred.
it is everything else that is concerning

 

So the battery was fully charged both times but one time it started and one time it didn't?If so i would check your wire connections at the starter and any other connections related to the starter!!

 

Would a bad connection to the starter cause all lights and accessories to be down? When it wouldn’t start I had absolutely no power.

 

Not sure but sounds like you had a bad connection somewhere!!

 

In a related question …if the BMS (battery manages system is not reset immediately after installation of a new battery, can you do it a few days after? Will it hurt the battery if not done immediately?

 

No, not resetting the BMS' battery in service counter value will not hurt the battery. It's not really recommended to do it after time has passed since the battery was replaced, however, a few days later is not likely to matter in the overall picture.

In the 2018 F150 owner's manual, it does not state anything about performing the BMS' battery in service counter. Resetting the BMS' battery in service counter is something we, in the community and Ford people, know about but it is not common public knowledge. Again, it's not even listed in the owner's manual for steps to do after a battery replacement yet other things are (idle relearn, window reset, etc.,).

It is believed that the BMS will, in time, assume the battery was changed. The BMS performs regular monitoring of the battery.