NOT Normal P Lock Malfunction - ONLY Happens Over 80 Degrees. Never When Cooler

Thanks for the explanation. That all makes sense. So it seems that by my readings there's an open circuit in PCON and PPOS. Still have no idea what the fix is, unfortunately.

I actually found a Prius specialist about an hour from me. They know the P con error, but have never heard if it being caused by heat like mine does. I'm taking it there next Wednesday. They'll do a diagnostic for $180 and we'll go from there. They have a bunch of Gen2 parts and ECUs in stock for $50, so if it's one of those they should be able to swap it out for me. Hopefully!

 

SOLVED!!!!

I took it to a local Prius specialist and they eventually found a bad wire to the transmission resolver plug. They said it was very difficult to find, that they'd OHM'd every wire multiple times, and it took them a couple of weeks of testing to determine that was the issue. Once they fixed that, the P lock error went away.

But apparently, they fried the parking brake control module in the testing/fixing process, so when they turned the car on it would short out and fry an ECU. It took them a couple of weeks to figure out that was the issue, but once they replaced the parking brake control module then the car was all good.

I highly recommend autobeyours.com / Frontier Automotive in Scottsbug, Indiana. They were very fair with pricing, considering how much time they put into it. They're all great and friendly and they are an honest shop. They specialize in Prius, but work on all makes and models too.