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P0446 and Techstream "TBP" Fail

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by fragglestickcar, Apr 4, 2018.

  1. fragglestickcar

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    Can't shake a P0446 for several months now.

    Techstream Engine and ECT Live shows a single failed test labelled "TBP". I believe this stands for Tank Bypass, which is another name for the purge flow valve. The evap system naming is very confusing since each valve goes by several names, and some of them even conflict.

    Here is the graph of vapor pressure when running the Techstream Utility: Evap System Check (Manual).
    img.jpg

    I have read the TIS, and am not about to go through the step-by-step because for one thing I don't have the "hand-held tester." I've read in a separate thread that people have just gone ahead and replaced the VSV and canister. I'm inclined to do the same unless someone has a better idea? Thanks.
     

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  2. fragglestickcar

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    I can't do it. I unbolted the two straps holding up the enclosure marked "A 64", but I really need to completely remove it. Just letting it hang didn't give me enough room. I couldn't get a good enough angle on the 10mm bolt circled green. I started to strip it, and stopped. Funny how everything looks so accessible in pictures, but once you're contorted under the car, it's all so very hard to get any leverage. Not about to spend 1-2k at the dealer, so seems I'm gonna have to live with P0446.
    wide.jpg bolt.jpg
     
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  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    It seems you have access to Techstream running on a laptop, which is the successor device to the handheld tester - for your future reference.

    It also seems you are having trouble accessing the potential failed parts, so I guess it doesn’t matter with this particular problem.
     
  4. fragglestickcar

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    FWIW, the TechStream freeze frame and failure data for anyone with a similar problem.
     

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  5. Erik Owens

    Erik Owens Member

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    That is not a good graph. The reference lines are good but the middle graph line that looks like a shark tooth point should be below the two lower flat spots on the graph. The reference is the .020" leak orifice inside the canister. It references the orifice twice to get the baseline and double check the base line.
     
  6. VFerdman

    VFerdman Senior Member

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    I've been living with the recurring P0446 for a while now. I noticed that after replacing my dying 12V battery the code stopped showing up for a long time. It finally did show up after a few months rather than a few days as before I replaced the 12V battery. When it showed up I put the now almost new 12V battery on a trickle charger overnight and again, the P0446 did not re-appear for a relatively long time. Now I am beginning to get it again. Will try the trickle charger trick again and see. The trickle charge trick may be masking the real problem, but I am really in no mood to go replace parts that really only make the government happy and do not effect the everyday performance of the car. So I just clear the code and go on with life. If the trickle charger trick works for me again I will let you know. My theory is the purge valve is failing and anything but a very strong 12V battery at good charge does not provide enough juice for the test that the car seems to perform when it's parked at night. It's a theory, not a piece of knowledge. I just observed a pattern with the 12V being weak and P0446 re-appearing.
     
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  7. fragglestickcar

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    I do not know. Agree the flat spots are baseline quiescent states but don't know why you think the techstream test (whatever it's doing) should result in vapor pressure dropping below baseline when it's turning off and on the valves.

    I happen to believe the wave form is correct because it's consistent and because the techstream manual test doesn't subject the system to the same rigorous "rate of decay" tests that the car's internal test does. If anyone with a techstream wants to clarify the matter, please run Utility: Evap System Check (Manual) and publish your results!
     
    #7 fragglestickcar, Apr 24, 2018
    Last edited: Apr 24, 2018
  8. fragglestickcar

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    Glad to see another chatter with P0446. Are you aware the evap test can take weeks to complete? The car needs to run the test at least a couple times for the evap MIL code to clear and its decision to run the test will depend on temperature while parked, current temperature, how long since the last "drive cycle," and fuel tank level. The timing of the incidence of P0446 in relation to your 12V experiments seems spurious and would be very hard to reproducibly test, but what do I know. Thanks, brother.
     
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  9. VFerdman

    VFerdman Senior Member

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    I hear you. My 12V experiments may be total coincidence. I have no idea how the test works. Thanks for enlightening me. I think it's a bit of a BS thing to test for and therefore just do not care much if it fails. I think I loose more vapor to atmosphere every time I fuel up at the gas station than anything escaping my gas tank. Some EPA requirements are a bit ridiculous. Especially for a vehicle that produces a small fraction of emissions that say an Econoline van is allowed to produce.
     
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  10. padroo

    padroo Senior Member

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    With reference to the OP removing hard to get to parts. I have been stared down by jobs like yours and then come back to them a different day I am able to complete the task with a new attitude. In other words good luck.
     
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  11. fragglestickcar

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    Update: it's fixed for $600.
    I found a for-parts prius on craigslist, and negotiated the repair with its owner for $500. Unfortunately, the fellow kept postponing the job until I sweetened the deal to six hundred.
    It took him 2.5 hours to remove the canister from the donor car. Most of the time was spent attempting to cleanly unbolt the thing, but he discovered it was impossible (see first post). A reciprocating saw was applied to the metal mount points. This preserved the plastic loops on the donor canister body.
    It took another hour to replace the faulty canister. Note that unlike the donor canister, the faulty canister is cut on the plastic body itself instead of the metal mountpoints on the car (see picture). Preserving the metal mountpoints allows for ziptie'ing the donor canister. The exception is the upper left cut on the metal bracket housing the vacuum valve. This is okay since the donor canister should have its own bracket.
    The hoses were readily pulled off without much fuss. He used some nice bent long nose pliers, but I'd imagine any set of pliers would do.
    While I paid close to dealer rates for the fix, I did reap the benefit of being able to observe how it was all done. And yes, it was definitely something I could have done. I just needed the courage to saw things off. If this helps anyone else out there, then it was all worth it.
    canister.jpg
     
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  12. bisco

    bisco cookie crumbler

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    i don't think i've ever seen this before, thanks!(y)
     
  13. VFerdman

    VFerdman Senior Member

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    I am really hoping I can pass my state inspection at the end of this month by just clearing the code. If I have to go through this nonsense and expense to replace a non-essential part I may be very upset. how much does a new part cost at the dealer?
     
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  14. fragglestickcar

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    @VFerdman Like you (and probably millions of others), I've passed inspection by disconnecting the battery a few days before and having the emissions test remain incomplete. There are many differing opinions on whether an "incomplete" would pass (see Is it possible to pass NY state inspection Emissions with EVAP system NOT READY? - Maxima Forums). My advice is to go to the same garage that passed you in the past. I know my local chop shop passed me without much ado.

    Having said that, it is a wonderful feeling to not have the code anymore. A new canister and valve (you need both!) will set you back probably $300 at the dealer. Used ones on ebay can be found for less than 100, but watch out for false labelling as many of them claim to be prius canisters but upon closer inspection aren't quite the same. Part number is 77740-47050, to be sure.
     
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  15. VFerdman

    VFerdman Senior Member

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    Thank you for the info. You said you fixed it for $600 and I thought that was a bit steep. Now you are saying it can be done for much less. Did I miss something?

    Also, this is going to be my second inspection. I bought the car last July and had to do an inspection within 7 days of registration. It passed just fine, but there was no code displayed at the time. The PO may have cleared it or, more unlikely, it wasn't a problem yet. I got the code soon after I bought the car and it kept coming back ever since. I do clear it with Torque Pro app, but it comes right back. I will attempt to pass inspection soon and if the car fails I will need to start looking into it. Other than that I will just live with it. In my opinion, it is a completely pointless code that does not effect anything, including, as intended, the environment. This is one of those mandated BS requirements that was met by manufacturers happy to collect $$ for bogus, but very expensive "repairs".
     
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  16. fragglestickcar

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    The parts are $50-300 for used and new. Labor shall vary.

    My trajectory is identical to yours -- I bought my '06 last August from a previous owner who likely cleared the code. The code came on after a week. I disconnected the battery and passed inspection.

    Someone should correct me, but my experience is the code returns within a couple drives if you clear using your typical obd2 scanner as opposed to disconnecting the battery. Everything I've read regarding the internal test having to wait for a complete drive cycle, a half-full tank, and the right outside temperature only applied after disconnecting the battery.
     
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  17. Hfabiani0127

    Hfabiani0127 New Member

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    It killed my battery slowly. Died on the road. Now I cant even pump gas without turning the pump nozzle upside down. My code was on for about 7 months.
     
  18. VFerdman

    VFerdman Senior Member

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    Can you please explain why you think the P0446 code killed your (12v?) battery and why you can't pump gas without turning the nozzle upside down? Your statements do not seem to follow from one another. Do you think the code caused your battery to die? And is making you have to turn the nozzle upside down? I am confused.

    I am still getting the code. Had to clear it to pass inspection and then it came right back. I am also having trouble getting the pump to pump more than a few gallons at a time, but that's due to the bladder being what it is and I do not believe it has anything to do with the code (but I may be wrong).
     
  19. exstudent

    exstudent Senior Member

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    1) Part lasted 2018-2007= 11 years
    2a) Amortized cost (year): $600/11years = $54.55/year
    2b) Amortized cost (month): $54.55/12 = $4.55/month (cost of a grande/venti latte)
    2c) Amortized cost (mile): $600/your odomoter reading = $cost/mile

    Compare that cost against tires, that you replace how many times over the course of vehicle ownership?
    Sure would be nice if all the tires purchased only cost $54.55/year or $4.55/month or $.00001/mile.


    Let's put the conspiracy theory to rest.

    Manufactures don't want to add to their vehicle costs w/ unnecessary parts. If they could, they probably would not have that part. Remember, post #16 says a new part is $300 retail/online; Lets just say this part costs Toyota $25. Now if this part was optional, every Prius would be $25 MORE PROFITABLE.

    If the sales of Prius for the Gen2 years are correct from Carsalesbase, then 748,646 Gen2 Prius were sold.
    upload_2018-9-12_21-29-35.png
    748,646 x $25 = $18,716,150 lost revenue for an optional/unnecessary part.
    Now ask yourself, would a publicly traded company that has to answer to share holders choose an optional part, foresaking $18.7MM in additional profit? If this was your private company, would you choose an optional part at the expense of $18.7MM in profit?

    I don't have the sophisticated testing equipment to measure vehicle emissions to see how much of an impact (big or small) this part has. But, the engineers and BIG BUDGET research and development department, driven by Science and facts, not alternative facts, led Toyota to add this part, costing the company $18.7MM in additional profit.

    Remember, companies want to maximize profit and always fight/lobby for no regulation or looser regulation that is to their benefit and profit.
     
  20. fragglestickcar

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    Rereading your remarks, the code not appearing right after replacing the battery is consistent with all obd tests getting a full reset and the temperamental evap test having to wait for the right conditions (see post #8). Again, my experience has been that simply clearing the code via the obd scanner won't do a full reset (see post #16), and the code quickly comes back. I would be surprised if the incidence of the P0446 code has anything to do with the level of charge on the 12V. Glad to see you passed inspection anyway.
     
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