Not getting spark ignition, codes P1684 and P0012

Can you confirm that the P0012 was not a different code like P0120?

The P0012 code is for a camshaft position sensor issue which is typically on vehicles with variable cam timing and this engine does not have that system.

Then the P1684 is just telling you that you lost 12 volts to the TCM which is part of the PCM. However, the TCM portion has its own power and ground, so this is what was lost and not the power to the PCM portion.

This is important because it would cause issues but most likely not the loss of ignition.

Which means we need to find out how you know it lost spark. Does the vehicle not start now, and you removed the plug wire to check for ignition and there is none?

If this is the case, it could just be a crank sensor issue.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

Let's start with this info and we can go from there.

Thanks