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2008 Prius "Park Button" Not Working

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Prius Newby, Jul 13, 2024.

  1. Prius Newby

    Prius Newby Junior Member

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    The Park Button won't engage park (and therefore, disengage?), and when I shift into Reverse or Drive, the transmission almost immediately shifts back into Neutral (as indicated on the digital gear indicator).

    About 10,000 miles ago I drained and refilled the transmission twice with Toyota WS trans fluid. No leaks.

    No odd dash lights are illuminated.

    What is the problem?
     
    #1 Prius Newby, Jul 13, 2024
  2. bisco

    bisco cookie crumbler

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    how is the 12v health?
     
    #2 bisco, Jul 13, 2024
  3. ChapmanF

    ChapmanF Senior Member

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    A scan tool will probably show some C23xx trouble codes. Those would be helpful.
     
    #3 ChapmanF, Jul 13, 2024
  4. Prius Newby

    Prius Newby Junior Member

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    Replaced the 12V battery in March, though haven't measured voltage since this Parking Button problem started yesterday.
     
    #4 Prius Newby, Jul 13, 2024
  5. Prius Newby

    Prius Newby Junior Member

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    I have simple OBD2 reader, will this read the "C" codes you mentioned?
     
    #5 Prius Newby, Jul 13, 2024
  6. ChapmanF

    ChapmanF Senior Member

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    Simple way to find out....
     
    #6 ChapmanF, Jul 13, 2024
  7. Prius Newby

    Prius Newby Junior Member

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    True, it's pushing 100 degrees here so I'll check in the am and report back here.
     
    #7 Prius Newby, Jul 13, 2024
  8. mr_guy_mann

    mr_guy_mann Senior Member

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    #8 mr_guy_mann, Jul 13, 2024
    Brian1954 likes this.
  9. Prius Newby

    Prius Newby Junior Member

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    Update:
    My OBD2 reader didn't indicate any codes.

    Today the parking button is functioning 100% correctly, and the transmission is shifting into gear and staying in gear as it should.

    WTH?
     
    #9 Prius Newby, Jul 15, 2024
  10. bisco

    bisco cookie crumbler

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    get a free load test on the 12v at many auto parts stores
     
    #10 bisco, Jul 15, 2024
  11. Prius Newby

    Prius Newby Junior Member

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    I followed a YouTube video and checked the 12V battery...Checked out great.

    I am baffled, and open to more ideas on the cause and how to permanently resolve this "phantom issue".

    My wife is about to drive the Prius 100 miles tonight, so she will give me a report.
     
    #11 Prius Newby, Jul 17, 2024
  12. mr_guy_mann

    mr_guy_mann Senior Member

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    If there was something causing a problem, most of the ecu's will retain "history" codes (for awhile, so long as the 12V battery hasn't been disconnected), even if there are no active problems or warning lights on.

    You would need a capable scantool to check this. Or you can wait until it causes more problems - possibly somewhere inconvenient.

    Posted via the PriusChat mobile app.
     
    #12 mr_guy_mann, Jul 17, 2024
  13. Prius Newby

    Prius Newby Junior Member

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    When my wife tried to leave for her 100 mile drive the Park button and transmission acted up again, same weirdness as before.

    At this point I plan to make an appointment at the nearest Toyota dealership for diagnosis.

    Thanks to all for your input so far. I will report back here after I learn something from the dealership.
     
    #13 Prius Newby, Jul 18, 2024
    bisco likes this.
  14. Prius Newby

    Prius Newby Junior Member

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    Update: Despite the fact the engine battery checked out as okay, I replaced it with new (Napa brand with 3-year warranty) this morning. Now all systems are working...The battery (Exide brand with 4-year warranty) I replaced lasted only 3 months, and the one before that (Exide brand with 4-year warranty) lasted12 months.

    Again, no CELs are illuminated.

    I canceled the appointment for my Prius at the local Toyota dealer.

    Any ideas why my Prius seems to frequently need new engine batteries?
     
    #14 Prius Newby, Jul 26, 2024 at 11:09 AM
  15. mr_guy_mann

    mr_guy_mann Senior Member

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    Personally (professionally), I don't like Exide batteries. Napa's AGM batteries are usually made by East Penn manufacturing, and are my second choice behind OE.

    IF (if) the 12V battery is "bad", then it could be poor quality parts, or the use of the car vs sitting isn't enough to keep it charged, or there could be excess current draw on the 12V when the car is turned off. Without testing it's all guessing.

    Since I assume your "shift" problems occur when the car is ready (and the DC-DC converter supplies 14V to the car), then the battery is unlikely to be the problem.

    If I actually wanted to figure out what was going on when my car was misbehaving, then I would have a capable scantool to look at data from the hybrid control and "transmission control" ecu's. In particular, I would look at data when it was working so that I could see what's different when it's not.

    Otherwise I would just be sitting around making guesses and waiting for it to act up again. (maybe that's just me).

    Side note, does the brake light switch work reliably?

    Posted via the PriusChat mobile app.
     
    #15 mr_guy_mann, Jul 26, 2024 at 1:05 PM
  16. Prius Newby

    Prius Newby Junior Member

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    I appreciate the idea of using a good scan tool while the car is operating as it should, and then again if (when?) the car is not acting as it should. I am just not excited about spending about $1K on a decent scan tool.

    Yes, as far as I know the brake light switch is reliably working. When my wife drives our Prius away from our house and she applies the brakes at her "first turn", the brake lights illuminate. Why do you ask?
     
    #16 Prius Newby, Jul 26, 2024 at 3:28 PM
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