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2007 Gen2 Prius ongoing nightmare - Problem w/ P mechanism - HV code P3102

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by gwydion_black, Aug 9, 2023.

  1. gwydion_black

    gwydion_black New Member

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    Hello Prius Chat,

    This is a tale but I want to include all the info I can remember. I'm a big DIYer and I am at my wits end with this situation.

    Long time lurker since getting our first Prius back in 2018. Loved it so much that when it came time to replace our other vehicle, we got a Prius.

    2007 Prius gen ii bought back in April with 130k miles. Rigorous test drive and seemed perfect. Took it home and worked fine until the end of May, commuting and long trips. Put about 500 or so miles on it and then after a long weekend of no use, went out Monday morning and got the "Problem with P mechanism" error and could not shift to drive.

    Quick research on that showed it was not a good error message to receive on these.

    At first I was able to fix it by letting the car sit off for 15 minutes and trying again. When that stopped working I had to unplug the 12v battery for 30 mins, and then it would be good to go. For awhile it would only show up like once every other week. In early July it kicked on and this time would not go off. Left me stranded down the road from my house unable to move it.

    Did the research and found 12v battery most likely cause. Went out and got a new one, replaced it myself, car started up and all was good. Drove it for a week and then the error came back, could not clear it again.

    Got an OBD sensor, multimeter, and Dr. Prius app. Pulled codes P3000, P3102, and P0A80. Bad hybrid battery.

    I work in tech so decided to try to fix the hybrid battery myself by replacing bad sections. It was tough but not too difficult in my opinion. Got refreshed battery back in. Prius ran for 2 days, coded out again with the P mechanism error, same codes.

    Got a professional to replace the hybrid battery with a refurb. All codes cleared! Hallelujah! Test drive fine. Back to work for 3 days - warning lights come back on dash. Code P3102 is back. Transmission control module failure. Makes sense with the original issue so maybe it is two fold?

    Replaced the TCM. Glorious working Prius for 2 whole days and then get the P mechanism error. Only started after the code and light reappeared for a few hours. Can't clear it or it comes right back. Can't shift car. Car won't go into ready - same as before but still only pulling code P3102.

    Throughout this all I also replaced some fuses and only issue I noticed regularly is a parasitic drain on the 12v that was more than should be. In the beginning it would die on me after not driving dor 3+ days and would have to charge it. Noticed that even with Prius off, you could actually watch the voltage drop on the battery. Also noticed that it was not the original 12v, replaced in 2017. Even with the new battery this still occurs, but not always which makes no sense to me. If left sit for a few days even the new battery will drop to <6 volts.

    When the issue returned the latest time, the first thing I checked was the 12v battery and voltage was actually fine at right around 12.5. Seems to charge fine when the car engine runs.

    I don't know what to do next. I dont have the funds to have the car experimented on and I have seen horror stories of thousands in labor to diagnose this problem only to have it not Be fixed.

    Can anyone help me out on what next steps might be here?
     
  2. bisco

    bisco cookie crumbler

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    could the refurb be bad?
     
  3. mr_guy_mann

    mr_guy_mann Senior Member

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    What are you using to pull codes? P3102 sets in the Hybrid Control ecu. It should have 1 of 7 INF sub-codes that would help narrow down the specific problem area.

    Can your scantool pull codes and data from the Trans control ecu?

    If not here is a thread that reviews several scantool apps and devices. Some are capable of scanning all systems on a Gen2 (and getting INF codes).

    You might need to use a scope to view what's happening to the circuits mentioned in the various P3102 workups.

    https://priuschat.com/index.php?posts/3290690

    Posted via the PriusChat mobile app.
     
  4. gwydion_black

    gwydion_black New Member

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    The hybrid battery itself is testing fine all around in all apps I've tried.


    I have a Veepeak bluetooth scanner. When I check the freeze frame in Car Scanner app, it appears to work but the code shown is p0000. Does this mean my adaptor cannot read the INF codes?

    I checked the page but it still isn't clear to me. What is the cheapest option I can get to scan those codes?
     
    #4 gwydion_black, Aug 12, 2023
    Last edited by a moderator: Aug 13, 2023
    bisco likes this.
  5. gwydion_black

    gwydion_black New Member

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    To update:

    Had the 12v unplugged for the last 2 days while I backed away from the situation for a minute.

    Plugged it up today and no codes, went right into ready mode. Engines fired up. Tested 12v at 12.3v before I started.

    Let it idle for 30+ minutes and nothing. Took it for a 3 mile drive, parked and indled for another 10 mins. Got big in and as I was pulling away coded hit. P3102. Red exclamation in triangle, exclamation point in circle, and VSC light all on, little ribbon across the top of the screen with an exclamation point.

    But I was able to drive it the 3 miles back and park it at home again. It did not yet do the "P lock mechanism error" but that is usually what comes soon after.

    Interestingly enough it seems to drive better than fine when it is working, I just dont get it.
     
  6. bisco

    bisco cookie crumbler

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  7. mr_guy_mann

    mr_guy_mann Senior Member

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    Car Scanner is very limited on a Gen2 Prius. It can (sort of) scan the ECM, hybrid control, and HV battery ecu's. AFAIK it only has freeze frame for the ECM.

    Some of the other apps/devices are more capable. Also more money, but the added functionality is worth it to some.

    Posted via the PriusChat mobile app.
     
  8. gwydion_black

    gwydion_black New Member

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    Update:

    An update to this situation. I regret ever buying this car at this point, especially from a private seller.

    I took the Prius to a Toyota Dealership. They had my car for over 2 months. It took them 3 weeks before they gave me a rental free of charge because they couldn't find the issues. They tore the car apart, replaced nearly all of the ECUs, checked all the wiring, and no go. During that time the 12v drained on them multiple times (brand new 12v I put in) and they said it needed replaces due to a bad cell. I did the warranty with Advanced Auto and they installed the new one.

    Eventually they said screw it and Toyota techs told them that it was most definitely a wire issue and they would be able to bypass the issue by rewiring one or more of the ECUs. They didn't exactly tell me which ones, but the codes were all clear and about $2000 later I was back on the road in November.

    Car was fine through Nov. At the end of November I got the codes for a bad hybrid battery (which was replaced as well). That was under warranty so I got that replaced again.

    Car was fine. Used it for all our long distance December travel. A couple days ago I went out to start the car in the morning. Came back 10 minutes later to find the car was off and was looking like the 12v was dead. Very dimly lit check engine line on dash, no power to windows or trunk, ect. Checked the 12v with a multimeter at it only said 4V. I had to double and triple check it because how does the vehicle have enough juice to start up and 10 mins later have only 4v left in the battery?

    Charged the battery. Started the car. "There is a problem with the P lock mechanism". Hybrid code P3102 - the same damn thing it was doing.


    I almost cried when I saw it. I don't know what to do. My love of Prius has soured after this encounter and I am at a loss. I've never has an issue this bad with any or my past vehicles.
     
  9. ChapmanF

    ChapmanF Senior Member

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    What a depressing story. The P3102 is probably going to keep coming back until somebody knuckles down and diagnoses what specifically is causing it, and fixes that.

    Most DIYers want to skip the diagnosis part and go swap something; they'll see the fortune cookie for the P3102 code has the words "transmission control ECU malfunction" so go change that ECU and hope for the best.

    You'd want to think dealerships would be where careful diagnosis would really happen but, as your experience shows, the reality is too often different. Dealerships also hate careful diagnosis, because people who are good at it have lots of career opportunities besides wrenching at a car dealer, so they're hard to hire, careful diagnosis takes serious time, and the dealership can ring up more money faster doing other things. Plus they get to play a turbocharged version of the throw-parts-at-it game and use your money to do it.

    If you want a decent chance of finding the P3102 cause yourself, you should really think about checking the list of scan tools mr_guy_mann linked to several posts up, to get one that can show you the P3102 subcode. There are seven of those and they mean different things; if you don't know which one you've got, you're really blindfolding yourself.

    It also seems like you've got a parasitic drain issue clobbering your 12 volt battery, and that might be the thing to get to the bottom of first. The park actuator issue can be influenced by that, because unparking and parking are often among the first things you do at startup and last at shutdown, when the DC/DC converter isn't carrying the loads and the battery needs to supply the actuator current.

    So if you find and eliminate that weird drain so your battery isn't conking out every time you turn around, that will at the very least annoy you less while you pursue the P3102 issue, and it might even help.