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Pesky problem with transmission "P" lock, red triangle, or parking pawl.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Andrew_Ph, Dec 19, 2017.

  1. Andrew_Ph

    Andrew_Ph Junior Member

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    I have been running with this problem for literally 1,000's of miles, to mexico and back even. At first the red triangle and display of "There is a problem with the transmission P lock mechanism..." came on when the weather was bad or wet, then would eventually go back to normal. Then it was all the time. briefly once it went back to normal when the weather was colder or something. I have read and tried almost everything related to the battery and wiring. The battery checks out fine. Also tried using my fairly new truck battery jumpered in instead. Also read something about a possible bad wire between the 7.5A fuse in the engine compartment and the wire connectors on the lower passenger inside, so I jumpered in another one. Also checked and cleaned all battery terminals in the back and tightened leads. None of this changed anything.
    Realize I actually have no problem with the car moving or going in and out of park.
    Why it concerns me, besides the annoyance, is that I cannot drive for uber or lyft without getting it inspected, and it wont pass with that there.
    Wondering if anyone has ever really figured out what the issue is. I could possibly take the parking pawl out and inspect it and the wiring, but it seems in a very difficult place to unscrew 3 hex bolts or something.
     
  2. zsolar

    zsolar New Member

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    You can't get to the pawl without removing and disassembling the transmission. You can take off and inspect or replace the actuator motor, but I don't know if that would be helpful. I recently tore a Gen2 transmission apart just for fun- that motor seems very robust, so I'd keep looking into the electrical parts.

    good luck
     
    #2 zsolar, Dec 19, 2017
    Last edited: Dec 19, 2017
  3. ericbecky

    ericbecky Hybrid Battery Hero

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    Super easy to replace when the transmission is out of the car.
    A huge challenge when it is in the car.
    The top bolt is the hardest.

    Contact your local dealer. Find out how much labor they would charge to replace it.
     
  4. zsolar

    zsolar New Member

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    The dealer would charge a lot of money since that part is super expensive - around $400. Better to struggle with the bolts and put in a used one. I'm sure it would be a little difficult to replace since I had a hard time just removing the electrical connector from that actuator when I removed my transmission.
     
  5. Andrew_Ph

    Andrew_Ph Junior Member

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    sorry, I meant the actuator. I would not try to pull out the actual motor/pawl.

     
  6. Andrew_Ph

    Andrew_Ph Junior Member

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    I am still thinking it may be some electrical connection, otherwise why would it have started doing that only when there is wet weather? The other reason could be the actuator motor is getting old and slow and not sending a signal to the ECU in the alloted time.
     
  7. VFerdman

    VFerdman Senior Member

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    How is the health of your 12V battery? If it's weak, the car will throw codes and parking system errors. I just went through this. Replaced the 12V battery and all is well.
     
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  8. jdenenberg

    jdenenberg EE Professor

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    +1 as a low 12v buss will often cause the "parking pawl" code since it can't supply enough current to the pawl actuator.

    JeffD
     
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  9. Andrew_Ph

    Andrew_Ph Junior Member

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    seems like hooking up a battery charger in trickle mode ought to solve it then, but it didnt. I just put it in diagnostic mode, and it said 12.2V before starting. 11.7V momentarily while starting, and 14.2 afterwards when the charging system is up.
    Seems starnge after all that it could be a voltage problem, or not getting enough current. The only other possibly seems to be some kind of wiring.
     
  10. VFerdman

    VFerdman Senior Member

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    Trickle charger is not going to help if the battery is not holding charge. If it can't supply the current (too much internal resistance, say), it will have a problem with the parking system. The parking system is a motor, so needs a bit of current to spin up momentarily. The battery is very small to begin with as far as current capacity and "cranking amps" or current capacity. When it goes south it crosses the threshold where it is just not supplying enough current for some things. Parking is a known system that is sensitive to battery capacity. I also kept getting a P0446 code, which is an evap system purge valve check (when the car is off) and since new battery was installed have not seen that code or the parking error.
     
  11. Andrew_Ph

    Andrew_Ph Junior Member

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    Really, what a coincidence. I was also having a code like that, and having problems with the current evap emissions check, although the long term one they call the DTC or something comes out ok. I had been thinking about getting under the car above the fuel tank and pulling that valve out to check and/or replace it.
    That still makes me wonder why my truck battery doesnt do the trick, but it also doesnt check out perfect, and may be a little low in voltage, but i dont think there is anything really wrong with it, it has barely been used.
     
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  12. VFerdman

    VFerdman Senior Member

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    Do yourself a favor and change the 12V battery with a proper one. If you have a healthy 12V to try temporarily, that will work also, but make sure it is nice and fresh. Most of the car will work with a weak 12V battery. Mine was reading below 10V when I changed it, and the car started and ran, but was having the P0446 code pop up every other day and the parking system warning and very dim interior lights. After I put a new 12V battery in (I went with Bosch one, which was on sale at Pep Boys for $140 with free install), those problems have gone away. It's been about 10 days or so and no P0446 code or parking system warning. As I said, other than those two things the car operated perfectly well, but I knew I was on borrowed time with that 12V battery and chose to replace it before I got stranded. Sounds like yours is doing the same thing. I am not saying there isn't a bad connection somewhere, so make sure that's not the case. There is a long wire going from the + of the battery to the fuse box under the hood and the negative is just connected to the body near the tail light. Make sure those are nice and clean at both ends. There is a ground connection at the fuse box to the body as well. Check those for good contact. If that checks out, change the 12V battery and you should be good to go.

    Happy holidays!
     
  13. dolj

    dolj Senior Member

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    I tend to agree, while your battery is basically nearly fully discharged (i. e. flat), so as an aside, desperately could do with some loving kindness and have full charge, I don't think it is the villain in this piece. While VFerdman's point about dropping below 10 V is valid, I don't see that in what you report.

    You should do a load test (headlights on) on the battery after it is fully charged and then see how long it takes to drop to 11.5 V. If it drops within minutes, rather than several hours, just change it out. No point being emotionally attached to a bad battery. A lot agonise over the "to replace or not to replace" question, even me, but it is irrational. Do the tests and follow the evidence.
     
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  14. Andrew_Ph

    Andrew_Ph Junior Member

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    I have been wanting to follow up on this post. I bought a new [Optima Batteries YellowTop Dual-Purpose Battery, Group Size S46B24R, 450 CCA, Autozone: 2007 Toyota Prius 1.5L MFI HEV DOHC 4cyl Optima Battery, Part Number: 46B24R] for a really good price of $185, put it in, and... didnt solve the problem. I tested the voltage in various ways, using the diagnostic screen and torque, with both the old battery and the new one. As soon as I find that piece of paper I will post it. I seem to remember that with the car off and full headlights on, the old battery was down to about 11.2V. The new one was somewhat better, but I returned it. Both went slightly low when starting, somewhere between 11.4 and 11.8 V, then up to charging voltage.
     
  15. Andrew_Ph

    Andrew_Ph Junior Member

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    Oh, also, I still get codes for evaporative system vent valve, but I think I will need to replace that part.
     
  16. ChapmanF

    ChapmanF Senior Member

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    Hi ,

    For most of the thread, I didn't see you mention reading any codes, so I wasn't sure whether you were able to, and there wasn't much way to be of help without them ... but if it seems you can read codes, what are the ones you're getting from the transmission control ECU, and have you pulled the freeze frame data from it, and what did you get?

    Cheers,
    -Chap
     
  17. Andrew_Ph

    Andrew_Ph Junior Member

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    not sure what you mean by freeze frame, but I have never pulled any codes and neither has Toyota or autozone for anything related to the transmission. Only a P0446 - powertrain evap emission control system - vent control circuit, which I am pretty sure is the VSV valve. And occasionally a cam/crankshaft out of alignment, but thats very occasional, and I am sure its because of the valves (and maybe cam chain) being way out of spec.
     
  18. Andrew_Ph

    Andrew_Ph Junior Member

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    I can only conclude it is the parking lock actuator itself at this point.
     
  19. John McG.

    John McG. Junior Member

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    Andrew, what was the final resolve to his problem.
     
  20. Andrew_Ph

    Andrew_Ph Junior Member

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    There isnt one yet, because I took my battery in to get tested and it was ok, except a little discharged, and I have been looking for a used parking brake actuator, but no luck yet.