I've returned with a new problem sadly only a few days after resolving the previous. I'm now getting a P0685 code as of today, and the engine stalls when driving and the radio turns off and back on. I can crank and start the car fine, I've read if you can do this, it shouldn't be a bad main relay? However I'm uncertain on how to proceed and why it would happen days after it was working fine for a bit.

 

That code is for an PCM internal failure. Check your fuses again. Let us know which fuse (if any) is blown

 

Update to this. It was a loose positive battery terminal, luckily no damage to any components, tightened it up, cel light went away after about 3 minutes of idling and drove fine on two occasions so far with no issues.
Just hit 150k miles, did a transmission liquid drain and change, alongside power steering and brake fluid.
Not sure how the positive terminal got loose, however I'll keep an eye on it from now on.
Thank you again !