Code P1780 intermittent no start issue?

Engine always cranks easily, if it starts, it runs fine, runs smooth, never dies. The engine is more likely to start when cold, but not always. After driving, then stopping, for gas, shopping, etc, it often cranks fine, but fails to start (engine is warm, normal operating temperature). It makes no attempt to fire (no spark or no fuel). Sometimes, it will start after a few tries, sometimes it has to sit for 1/2 hr. Or so before it starts. Code read is: P1780 (PNP SW), I replaced the PNP switch and erased the code, still had the same problem and the same code came back. I saw something online about a failing crank position sensor can cause this, so I replaced the CPS, same problem. I have seen online that the GM pass lock security system can cause this, but in that case the engine is supposed to start, then die and then fail to start again and the "security" light comes on. It never does that, it either starts in less than 5 seconds, or it cranks freely without one cough.