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.

 

I'm sure they'd rape you out there for it. Many places here probably would too, even though the labor rate is much lower here.

I'm sure glad that it's finally fixed! Thanks for your help troubleshooting earlier.

 

My bad. I had too many things floating in my head when I wrote that. I meant that they fried the thing behind the black round cover at the back of the transmission. I think that's called the shift actuator? We discussed how they got that off and he said Snap-On Tools makes a specialty tool that allows you to get those bolts out and he said it costs $395 I think!

I think that's right anyway. I didn't write down what he said and I'm going from memory.

Thanks for your suggestions on it earlier!

 

Yes, it's a complicated issue potentially since there are several things that can cause that error. I had the manual and did the steps and found there was a likely ground fault sometimes, but the circuit was too complicated and had too many connections for me to figure it out.

And made more difficult to find because the error only happened when the outside temperature was over 84 degrees! The wire wasn't completely cut or anything else that was easy to find. The heat apparently caused the resistance in the wire to increase and thus caused the error message. They told me they Ohm'd every related wire several times and couldn't find it. I assume they could only find the bad wire when the conditions were right to cause the resistance to increase enough to set off the error. Every week when I called them they told me that they couldn't find it yet and how difficult it was. I'm glad they stuck with it and finally were able to fix it.