Your PNP is on it's last legs. One thing you might want to try to squeeze what you can out of it is to shift back and forth between P and L a couple times rather quickly. What this does is clean the contacts in the pnp, which does help in many cases. But from what you describe, it sounds like your PNP.

Sometimes, the PNP can go for a year or two before it really starts to give you problems when this starts to happen. However, sometimes, it's just a matter of days before you can't start your car because the car doesn't realize it is in P or N, which means the car won't let you start the engine.

You may not get a code btw. Also, sometimes, the PNP will show these signs without throwing any codes. My suggestion, learn how to read and clear codes, which from what I read, you already know, which is great. 'Cause you might suddenly find yourself unable to start the car until you do read and clear your codes.