Tranny jumps to Neutral when accelerator pressed, but shifter stays in "D".

Hello gang! I've got a "strange problem" happening to my GF's Gen I, 2002 Prius, w/ 225,000 miles and a 3-yr converted Gen II HV battery. While driving about fifty miles into her destination, the car suddenly Jumped out of Drive and went into Neutral, without any change in shifter position! It stayed in the "D" position. Unlike some or all of the other posts I've seen. After a flatbed tow home, I began to check out what the problem might be. I started it up and it ran as before, with some of the issues as before, like; the shudder at idle, and a slight accelerator miss or dead spot, but very slight and not to worry some. I started it and let it warm up a bit, without a problem. Then attempted to move it. I put it in D and it engaged. I took my foot off the brake and it wanted to move forward but needed a little throttle, which I gave it. Then surprisingly it disengaged and went into neutral and I could feel the difference. I gave it throttle again and it felt more unresponsive and unlike you'd expect if you were actually in neutral or park position; lower RPM, and poor response, but NO FORWARD EFFORT AT ALL. Placed it into park and gave it throttle, and it was fine. After more of the same, I figured I should check the tranny fluid and it was fine, about a half inch below the fill hole. The next day I drained and refilled it. That didn't change what was still happening. I played with it for while and noticed that if I ever so slightly pressed the accelerator, I could get the car to creep forward a very little but when I tried to roll over a twig and needed more acceleration, just a very little more, it popped out of gear again. Then I tried it on the downside of the crown of the road and made a small bit of progress. It allowed me a very little bit more throttle and speed,(almost unnoticeable, but I did go up the slight incline of the driveway.
The codes I pulled were P0304, P3125, and P0300. My first thoughts about this problem were a faulty 12V Bat., a faulty battery computer, or the tranny or body computer. So I swapped the battery puter with My 2002 Prius, even though I didn't see any revealing bad terminals on her's. No luck doing the swap. Then going off the code P3125, I went to the salvage yard and pulled an Inverter/Converter and did that swap. The code went away but not the original problem.
I think some sort of a Safety feature is being initiated by the car's system, that's not allowing it to drive normally, and think it might be one of the other 2 computers I mentioned above. I don't know. If anyone has something they think might solve this problem it would be much appreciated to hear about. Any questions or comments would be my pleasure to answer also. Thanks to all the great members here on PriusChat.
Sincerely ,
Tony D.
Covington, GA

 

GEEZ CHAP... I wish you had more to say about MY car problem; and leave the history class for another day. The codes are as stated. Now can you lend some of your knowledge to help solve or suggest an approach to begin diagnosing such a unique problem that a member is having? Thanks, and I appreciate any and all help from everyone.
Tony

 

Just got back on and see what you mean about Chap's directives. I apologize for my oversite. I only have an inexpensive scantool -bluetooth variety and it doesn't, (as far as I can tell) read sub-codes/INF codes, or are they different code tech?
Anyway, I just read a post by, Patrick Wong, Oct 1, 2010, and viewed that link about TechStream. I new about TechStream and thought the scan tool I have included TechStream. Wrong!
I also took Chap's info, about using my library for the CHILTONLIBRARY and found out they don't subscribe to it. However I did send a request to the proper individual(s) that my librarian told me about.
I don't want to spend a lot, but if someone has a used upscale scan tool, I'd be interested. Thanks for your message Brian.

 

Who is it you think deserves an apology? I don't see any Mark in the replies or comments and wonder if you eat Mexican too much, and if it also is what gets a stinky attitude to arouse in folks. "Ask and you shall receive". It never hurts to ask.

 

Thought about were or what would generate the problem and make it do what it's doing... Maybe a faulty APP sensor telling the computer to go into "Turtle" mode, or some other safety mode. It seems to definitely be from applying the pedal. It also may be the shift sensor, or maybe the (forgot the name) it's internal mech that senses where the magnets are, it's near the Parking Pawl. It may not know were it is pointing.
So far no response from the library for getting the "CHILTONLIBRARY". I send them another email. Thanks to all who help.

 

CHAP, you're right on again! I do owe you this apology and thank you for reaching out to me. I apologize for being ungrateful for your answer, and for criticizing a good attempt at helping me and others who did not realize the scale or breadth of the P3125 code's early confusive beginnings.

Indeed, I was and still am in a state, far beyond a bad day. But, I regress and won't delve into how or what I'm dealing with, that probably initiated my response to your full-bodied, informative Reply to my beginning Post. Please accept and forgive as I know in my heart, you will.

I'm happy I won't hear from the other critter. Hope he gets the broom out of his nice person someday.

 

nice person = where the sun don't shine!