When I had CEL in the past (and knew the provenance), I use to just reset the PCM by disconnecting the battery. Some of the unsolved problems would trigger a CEL only weeks later.

I just receive my OBD 2 scantool and I see I can reset the error codes. What difference it will make? Will the CEL(if problem not fixed) take again weeks to re-appear or could come back right away if the problematic conditions are met again? I would prefer the latter to troubleshoot problems...

Just trying to understand the difference between resetting the error codes by the scantool or by a complete PCM reset procedure.

if the problem is still not fixed, then the code will come back.