These are just some of my thoughts. I don't know what exactly could be wrong but feel free to try any of these.

1. Is the battery testing good? Is the CCA and voltage still okay?
2. Is the alternator charging the battery properly?
3. Is the starter working properly? Some places I think can test it for free as well you may have to check around.
4. Is there corrosion or anything on the terminals? Make sure the connection is tight and the terminals are clean.

Sorry if I couldn't help as much but hopefully someone more experienced can help out.

 

Could it be the battery without the battery light coming on? It’s reading 13.9v with car running nothing else on.

These are just some of my thoughts. I don't know what exactly could be wrong but feel free to try any of these.

1. Is the battery testing good? Is the CCA and voltage still okay?
2. Is the alternator charging the battery properly?
3. Is the starter working properly? Some places I think can test it for free as well you may have to check around.
4. Is there corrosion or anything on the terminals? Make sure the connection is tight and the terminals are clean.

Sorry if I couldn't help as much but hopefully someone more experienced can help out.

 

My 2015 charges at around 14.2 to 14.4 with absolutely nothing on, it may be alternator related but not likely.

There was a TSB about starters on our cars, and that could be the reason for the issue.

 

what is TSB?

 

I was wondering if it could be the starter because I recently got my alternator replaced I believe it’s like a refurbished alternator, but I don’t think it would have already went bad.

 

14V =/- .3V at the battery with the engine running is a good voltage

For TSB's; One place to start is here...

Vehicle Detail Search - 2015 TOYOTA COROLLA 4 DR FWD | NHTSA

www.nhtsa.gov

Scroll down until you find the 296 manufacturer communications.
Then pick a filter to reduce the number of things to scroll thru.
It's a lot to go thru

 

" I checked engine voltage and while running it’s 13.9v with car running nothing else on."
Check voltage when engine is cranking. Should stay above 10.5-11v.
If not changed battery.