2006 Prius codes P0420, 0171, 1121, and more rebuilt battery

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Wville, Apr 22, 2019.

  1. Wville

    Wville New Member

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    Hello all,
    I am new to the Prius world. I bought an ‘06 Prius (213k miles) from a lady and it had been her first car ever, yes I know, probably a bad idea. I got it really really cheap!! I’ve had it about a month, she’d had it diagnosed at Toyota and they said bad hybrid battery.
    So the first thing I did was have it rebuilt by a guy locally who owns a shop almost exclusively for Prius work.
    Here are the issues:
    When I first got it it would need to be jumped off, replacing hybrid battery seems to have solved that.
    Also replaced the 12V battery.

    It has never averaged more than 26 mpg on HWY, city, or both.

    Codes that have popped up are:
    P1121, P0171, P0420, P0A09, and P0A08.
    One rare time after I turned it off at the gas station, cranked again and it wouldn’t go into any gear besides neutral it threw code: P0AA6.
    I cleared the codes disconnected battery plug waited 10 minutes and it worked fine and 400+ miles later that code still hasn’t returned.

    So, the Prius guy told me the bad mpg and the 0171, and 0420 could be o2 sensors and possibly the CAT.

    So, maybe y’all can offer some advice.
    Since I got the car; terrible terrible gas mileage, and sometimes I have to do the reverse drive then slam in park trick to turn it off, but that’s pretty rare.

    Here are the repairs etc I have already completed:
    Rebuild hybrid battery
    Replace 12V battery
    Synthetic oil change
    Have run a fuel system emissions cleaner every other tank.
    Replaced combination meter because it would randomly not work at all.
    Replaced all filters
    Replaced o2 sensors
    New tires and alignment
    New info display screen

    And after all of this and through all of this the red triangle of death, the circle with exclamation and parenthesis around it, and the exclamation point in parenthesis they looks like troubled water or dots under it, all of those lights have remained on and consistent.
    Even when I use various OBD tools and clear the codes they come back literally immediately...

    The new combo meter had 181k miles on it, and the trouble lights are the same as the old one when it was working.

    For example today, I took the car on a round trip doctor visit to Baton Rouge so, about 240 miles, and it burned through over 1/2 tank of shell V Power fuel, and the information screen showed the current MPG between 23-26 whether I was holding t 60 mph or doing 80mph.
    Now of course when I’m slowing down or not pressing the accelerator it reads 70-99mpg

    My battery icon turns green on most trips, never fills all the way to the top, has previously turned blue and a purple ish color briefly before going back white or green.

    Basically, what am I missing besides replscing the CAT converter that is causing such terrible MPG?
    Also, I’ve read the coolant control valve could be stuck, this may be contributing to the dash lights, but wouldn’t cause poor MPG, and according to real-time diagnostics the engine coolant temp never rises above 190F even while driving 70-80 on the interstate.

    I’m not a super mechanic wiz, but if there’s instructions I can follow them, and do a great deal of my own repairs.
    I would take the CAT to a shop though.

    Any ideas or experience with these issues and how I might resolve the poor MPG? I could honestly care less about the lights being on, but it randomly not wanting to power off, or the one time it would turn on but only go into neutral those things are problematic as is the 19-25MPG out of what is supposed to be a hybrid fuel efficient car despite age and mileage lol.

    Thanks for any help!
     

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  2. SFO

    SFO Senior Member

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    Welcome to PriusChat!!

    Curious which OBD2 reader/app you're using, as you might want to invest in a mini-vci cable to retrieve the INFs for some of the DTCs you've listed (P0AA6 and P0A09). Knowing the INFs (aka detail codes or subcodes) can potentially help in narrowing down a problem.

    Once you've sorted out DTC P0AA6, you might want to check and replace the transaxle fluid, some think of it as cheap insurance.

    Here is the work up for DTC P0AA6 with the INFs 526, 611, 612, 613, 614 : https://attachments.priuschat.com/attachment-files/2018/04/145252_2006_Prius_RM_-_P0AA6.pdf

    Below is a nice visual for DTC P0AA6 (P3009) that might be of interest:

    2004-2008 Toyota Prius with code P3009 or P0AA6 and info code 526, 613, 614 | TOYO Headquarters

    [​IMG]

    Here is the work up for DTC P1121 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/2054m/cip1121a.pdf

    Here is the work up for DTC P0171 / P0172 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/2054m/cip0171.pdf

    Here is the work up for DTC P0A08 with an INF of 264 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21bpm/0a08264.pdf

    Here is the work up for DTC P0A09 with an INF of 591 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21bpm/0a09591.pdf

    Here is the work up for DTC P0A09 with an INF of 265 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21bpm/0a09265.pdf

    Here is the work up for DTC P0420 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/2054m/cip0420.pdf
     
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  3. TMR-JWAP

    TMR-JWAP Senior Member

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    WOW, Congratulations on owning a prius with the absolute lowest mpg I've ever seen. Maybe you've got some brakes rubbing/locked up. If you have an IR gun, shoot some tire/rim/brake temps a quick drive. If the cat were clogged that bad, I'd be surprised if you could hit 75+mph, but replacements are available for < $150. Looking forward to you keeping this thread updated with your progress. It should provide a lot of good insight. Wish you were near me so I could help.

    You really need to get techstream. You'd be able to get a lot of good info

    Also noticed your tpms light is on. Any chance tire pressures are extremely low? That will have some minor effect on mpg.

    Also, the light your seeing with the exclamation point in a circle surrounded by ( ) is the brake system warning light.
     
    #3 TMR-JWAP, Apr 22, 2019
    Last edited: Apr 22, 2019
  4. Wville

    Wville New Member

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    ———————

    Hey y’all.
    Thanks for all of the great tips. I’m going to have to research what to do for each of them because surprisingly enough each of you mentioned things I’ve not yet learned about or heard of.
    I used a traditional OBD tool you purchase at autozone or such that my father in law had on hand from last year. It gives very very little
    Information... I purchased a Bluetooth OBD tool that connects to my phone and I had to purchase the OBD Fusion App and the specific Prius software through the app. I can program it to give me a very large range of options and values on stats, performance, and I’m sure much much more. It also connects to Auto Doctor, which I thought was a steal for $19.99 for a year subscription.... turns out, the OBD Fusion app and software were the same price and are far more useful...

    I thought the one light was tire pressure but didn’t pay any attention to it because just 2 weeks ago I had all four tires replaced and an alignment done at firestone ($430) not too bad considering ... but I guess they didn’t reset the TPMS.

    On mention of the brakes, I did read of some Prius’ having a clicking noise when applying the break, I’ve noticed that happening more regularly, and loudly...
    I don’t think I have that gun you mentioned, my father in law might, I will definitely ask.

    I had firestone check all the fluids, however of course I double checked, and I had already done the synthetic oil change and filter myself so I know it’s current.

    If you’ll suggest the possible names of some values to pull from the OBD tool I’ll scan for them and post for your review.

    Is it normal, while sitting in park, car cranked, and a/c or defrost turned on, for the car to crank up the regular motor semi loudly every 3-5 minutes and run for about 30-45 seconds and then shut the regular motor off again?


    I also forgot to ask in my initial post if the battery and car exclamation point on the info display was directly related to the lights on the dash or if they indicated something different?
    Oh yes, A few more items ... I don’t really view them as significant but...
    cruise control doesn’t work at all, no indicator light etc.,
    And some steering wheel functions: specifically the defrost buttons do not work, so far I think all of the others do though.
    And finally, my key fob cranks the car, the key fits the door and unlocks the car... but, the buttons on the key fob and the button on the door will not unlock the car, and I replaced the batteries in the fob, and even attempted reprogramming it but every guide I found was to program a second remote so I didn’t really expect to be successful in that attempt.

    attached are screen shots of some of the sensors and values I already have set up in the OBD app. These values are while sitting in park with the car running.

    Please feel free to advise as whatever you’ve seen be successful lol.
    I too wish I was closer to more Prius gurus

    Hey! I guess I must of done something better... I just took the last pic of the info screen and average mpg, and it’s almost up to 28.... LMBO...

    Thanks again!
    Wayne
     

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  5. Wville

    Wville New Member

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    Oh wow! Thanks... that’s a lot of information and a lot of it got lost on me.. lol...
    I’ve posted some of the readings from the OBD reader and the app that I use. In the other comment. I read over those codes and explanations you’ve listed. It makes me rather curious because I’ve definitely got the car to over 80mph regularly, the o2 sensors are new, and I have no idea where that harness is that was mentioned in the DTC Codes you posted.
    I’m going to find a mini dvi cable and use that to get the sub codes I suppose. Is there a program needed for it, and hopefully I can use it with a Mac.
    Thanks
     
  6. bisco

    bisco cookie crumbler

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    it comes with tech stream, toyota specific diagnostic software. i think you're gonna need an old windows platform
     
  7. TMR-JWAP

    TMR-JWAP Senior Member

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    A couple more quick items I noticed in your photos:

    Your HV battery has 28 individual modules, but there are only 14 blocks. Each block is comprised of two modules. Any of your displays that are showing info for >V14 are invalid. I don't know what they're measuring, but it's not a block voltage.

    Your MPG display is showing 27.7mpg with 0 miles and none of the 5 minute markers populated. The first 5 minutes of engine run time are typically 23-27 mpg due to the warm-up protocol of the car. (for lack of a better term). After that first 5 minutes, the tune changes and MPG will significantly increase. My first 5 minutes just about always falls in that range, yet my current tank average is 54.8 mpg with almost 200 miles on the tank. I've been driving fairly conservatively on this tank, just experimenting with my daily 46 mile round trip to work. You may not have as much of a MPG problem as you think. When you get a chance (and probably after the HV issue is resolved) take a long ride on a flat road somewhere and hold a steady speed, see where it falls. You may be surprised.

    I wonder, since your mpg is staying fairly steady and similar to the "5 minute warmup" if the car is somehow stuck in that first phase? Just throwing out thoughts...
     
    #7 TMR-JWAP, Apr 24, 2019
    Last edited: Apr 24, 2019
  8. Hokie-Dave

    Hokie-Dave Member

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    If your tire pressure light flashes for about 30 seconds when you start the car up, then goes solid, that is telling you that one (or more) of your TPMS sensors probably need to be replaced (the battery inside them died).

    If you have a Harbor Freight near you, you can get one of the infra red temp guns for about $20 from there.

    And chances are Firestone did not check the transmission fluid since it is a sealed system. The transmission takes 4 quarts of Toyota WS transmission fluid. It can be a little pricey. If you decide to change the fluid, it is replaced similarly to a manual transmission, where there is a drain and a fill plug on the side of the transmission. You would fill it using a funnel and long tube or a pump.

    Sorry, but I can't be too much help on your other issues.

    dave
     
  9. Wville

    Wville New Member

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    Hi guys, okay,
    So I’ve ordered tech stream, we shall see how that goes.

    I’ve ready the A08 code could be the inverter or converter or even the pump for it.

    I bought the cat converter online for $60 and took to a muffler shop to have it installed, and they ran codes and checked system and said CAT was NOT bad or clogged. Said they would clear codes and I should drive it and return if the codes come back.

    So, I took the advice on driving it a distance on as flat of a road as I could get.
    I drove it on the interstate at speeds of 75-90mph from Covington, la to Biloxi, ms (approx 100 miles) I filled up at shell with 97 Shell V-Power, and also put in a bottle of Emissions full system high mileage cleaner, the kind that guarantees to pass emissions, I think this is just guaranteed for states like NY and CA and would force it to pass the OBD scan (this was not my goal, I just hoped it would clean some deeper parts and injectors etc)
    Anyway, after Biloxi, without refueling I drove to Bogalusa, la from Biloxi, Ms (approx 90 miles) at speeds of 65-80mph. Then back to a Covington from bogalusa (approx 36 miles)
    I have been relying on the MFD for MPG data, but this time I refueled and decided to run the calculations myself, and came up with 38.9MPG. Granted, on this trip the MFD, had increased to read (29.1MPG) which is the best it’s ever done.
    Before that tank, I would get at most 250-300 miles to a tank.

    So now, I’m back to having no clue what is wrong. On this tank I’ve since only driven short distances at speeds under 70, and have 170 miles on this tank and reading about 1 bar over half tank remaining...
    So MPG seems to be improving slightly...

    I disassembled the MAF Sensor and cleaned it, cleaned the Throttle Body while I was in there.
    Still have the A08, A09, and P0171 codes showing and they still come right back on immediately after clearing them.

    I have not yet checked the inverter coolant but I will be doing that shortly.

    On the MFD screen, I still see the Battery and the Car with the exclamation point, as well as the traditional red triangle of death and the other lights posted before.

    One piece of curious info, after I cleared the codes, my Bluetooth OBD reader tells me if the MIL (malfunction indicator lamp) is turned on or off, after I reset the codes it says the lamp is “off” even though it’s clearly on.

    Also, on the AUX battery in the back, there is the white plug that we can unplug to disable battery etc, but there is another very small single wire that runs to another much smaller white plug, any idea what this wire is for?

    The P0171 code is mainly emissions.... other than replacing the CAT, the Coolant sensor, and the MAF Sensor... I’m not sure what other emissions parts could be fixed...

    The trans fluid and other such fluids have not been changed to the best of my knowledge, but surely those would cause other issues like poor transmission shifts, overheating, etc ?
    Thanks again!
     
  10. exstudent

    exstudent Senior Member

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    This might still be a problem.

    It BEHOVES you to read the owners manual.
    Red Triangle w/ exclamation point = MASTER WARNING LIGHT (get codes read)
    Circle w/ exclamation point and parenthesis = BRAKE SYSTEM PROBLEM (STOP DRIVING THE CAR)
    Exclamation point in parenthesis looks like troubled water or dots under it = TPMS (Tire Pressure Monitor System), normally a a low tire/s. BUT, given your 2006 and the known reality that the batteries in TPMS seem to last 7-10years, multiple TPMS sensors are dead and require replacement; best to replace all four. It could also be that Firestone damaged a sensor when installing the new tires; I am more inclined to believe multiple sensors were dead before they replaced your tires. You should have gotten new sensors when you had new tires installed.

    upload_2019-4-27_23-3-13.png
    upload_2019-4-27_23-3-25.png
    upload_2019-4-27_23-4-49.png

    Bluetooth OBD devise and apps are toys IMO. 1) Can NOT read all Prius codes and Sub-codes. 2) Can NOT: bleed brakes, spin engine for compression check, and others. When your mini VCI cable w/ Techstream arrives, you will see how useful this tool is.

    Yes. The car will force the engine to turn on as needed so the HV battery does not run down.

    Car w/ exclamation point = problem with the Hybrid system: electric motor, Inverter, HV Battery, etc. Get the codes read with Techstream!

    Classic steering wheel clockspring cable has died. Read post #19 and decide which one is best for you (OEM vs fake).


    Good, you replaced the CR2032 battery in the FOB remote to rule out a bad FOB battery. The small mechanical key works. Hopefully you have the five digit mechanical key tag, to cut a clean key; vs a copy of a copy. Unfortunately all of this points to the most likely reality that the SKS Fob you have is a used fob that belonged to a different SKS Prius, thus the lack of SKS functionality for your car. This assumes the SKS function is ON, of course.
    upload_2019-4-27_23-36-22.png

    If you wish to retain SKS functionality, you will have to pay for a Toyota dealer RESET and RESEED procedure. Mobile locksmiths are unlikely able to do this b/c of the security licensing cost. Price shop dealers to see who will do it cheaply. Don't forget about discount coupons from AAA, Costco, AmEx, and online Toyota dealer service coupons. A RESET and RESEED procedure is the only way to get a used SKS FOB to work correctly on a SKS Prius. However, given the cost of this procedure (likely $200+), and the relatively small price difference between used and NEW SKS Fobs, it is best to get NEW SKS Fobs.

    Part number of a NEW SKS Fob might be 89994-47061; verify w/ your dealership or an online Toyota dealership.
    Camelback Toyota sells a NEW SKS Fob for $164.21; free ground shipping ($150 minimum) and no sales tax.
     
    #10 exstudent, Apr 28, 2019
    Last edited: Apr 28, 2019
  11. Wville

    Wville New Member

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    Well Guys... we will find out what comes next here shortly..
    I mentioned all of the repairs in previous posts.
    As I went to disconnect battery, yet again, for a hopeful fix to a random issue, I noticed this little white lead positive wire was disconnected/unplugged from its connector.
    I googled and researched. I found what it was and grabbed some electrical tape, and a little 18 gauge wire, and saudered the new wire to the micro terminal connector, secured it, and reinstalled it.

    1st improvement noticed:
    when I cranked the car,
    The break system light was gone !!

    2nd: The cruise control WORKS now!!!

    3rd: ran OBD codes, came back with the same DC/Inverter (08 and 09) and Sustem Lean 0171 code... except.....this time when I cleared the codes ... THEY DIDN'T COME BACK!!!!

    So I was literally so excited I had to share it before I even got out of the car LOL...
    Going to take it for a quick test run and heat it up see if anything comes back... hopefully NONE come back !!!
    Thanks for all the advice!
     

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  12. Wville

    Wville New Member

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    Hey again,
    So I purchased a new key fob, and you were right the SKS button was OFF. However, I got the new remote programmed and it starts the car, but when I attempt to program for unlocking I get the 2 cycles lock/unlock to indicate the program failed. I’m going to email the seller, I don’t believe it’s a TOYOTA OEM, but it works otherwise, it’s possible it might just be the new fob is faulty, and the fob I have was like you said a used fob programmed like I did before I bought the car.

    UPDATE: after the other day of repairing the sense LEAD connector on positive side of AUX battery, I’ve driven the car approximately 175-200 miles with multiple stops, starts, parking, driving hwy and city, and ZERO Issues!!!
    The only code that keeps returning is the P0171 and P1121 which I’d assume are related codes.
    So, I purchased the new control valve and will attempt installing it later this weekend.
    Thanks for any insights!
     

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  13. ericbecky

    ericbecky Hybrid Battery Hero

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    So you bought a New fob?
    Not Used.

    Did the first fob ever unlock the doors with the button?
    You kind of need to start there.
    If the first one does not unlock the doors you won't be able to use it to program a different key.

    If the first one never could unlock the doors, then you need to go to a locksmith, the dealership, or use techstream to go through reseed process. If doing it yourself you will need to purchase a seed code to use with techstream. Then you can do both keys at the same time.

    If you bought a new key fob and programmed it to the car, then you just turned it into a Used key and isn't much good to most folks anymore. Many sellers will not take back a key once you made it no longer new. Rightly so.
     
  14. Wville

    Wville New Member

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    Hey,
    Thank you for the information and advice! Yes, that would be correct I did purchase a brand new fob with a blank key inside, but also correct, it is now no longer new since I am programmed it to the car and the seller on Amazon would not except it as a return or even replace it. However, from what it sounds like that would not of solve the issue anyhow. Do you have any idea what the dealership or a locksmith or such would charge me in order to reprogram the remote to lock and unlock the car? Also, to answer your initial question when I purchased the car used, the remote fob that came with it would not unlock or lock the car is by the button on the fob. I have looked into purchasing light stream, and I still think I might; however, what is a seed code? And how do I use it with text stream to reprogram the remote Bob’ I have looked into purchasing LightStream, and I still think I might; however, what is a seed code? And how do I use it with text stream to reprogram the remote fobs?
    The only downside to light stream from what I can tail is that a Windows computer is required, I only own Mac computers. So I will need to swing by pawnshop or something and locate an inexpensive windows laptop or netbook in order to utilize light Stream. The only downside to tech stream from what I can tail is that a Windows computer is required, I only own Mac computers. So I will need to swing by a pawnshop or something and locate an inexpensive windows laptop or netbook in order to utilize LightStream.

    I will say, though I really do enjoy the Prius and the potential features that it offers, and even the way that it drives and handles, for the age of the vehicle there is so little information how to use, videos, or self-help support available even though they can around four years. There is a great deal of do it yourself and self-help guy made by other individuals, unfortunately, those are not always the most accurate resource. I am actively learning more and more about the car actually only logged on to the forum today to post a question about something else, so I’m glad that I saw your post. Please let me know if you have any idea about the pricing or have any tutorials or two to reprogram myself
     
  15. Wville

    Wville New Member

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    Model:
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    AAE0C056-34C0-4261-ACD8-D09C9579433C.png 8ABB5A64-9A51-4DE2-88B7-681F01429D54.png 29B0A065-77F0-42E4-9E4B-B6208D0831ED.png 601A9BB5-6931-4AA1-903A-EFE196E5EB8C.png 914A5BEF-0D2E-496B-A816-494A575F8968.png AF3C922C-7D53-4590-B66D-74E211F98032.png 6E9DFC6A-C987-48AF-AE5C-45FAA3664FA2.jpeg 2D12A23B-96A9-4A13-9369-9B4C8E999AA3.jpeg AAE0C056-34C0-4261-ACD8-D09C9579433C.png 8ABB5A64-9A51-4DE2-88B7-681F01429D54.png 29B0A065-77F0-42E4-9E4B-B6208D0831ED.png 601A9BB5-6931-4AA1-903A-EFE196E5EB8C.png 914A5BEF-0D2E-496B-A816-494A575F8968.png AF3C922C-7D53-4590-B66D-74E211F98032.png 6E9DFC6A-C987-48AF-AE5C-45FAA3664FA2.jpeg 2D12A23B-96A9-4A13-9369-9B4C8E999AA3.jpeg Update: all right guys, you all have been so very helpful over the past several weeks with my Prius and the issues. However, the error code P0171 will not stay gone for good, or so it seems. This week I finally got the chance to replace the coolant flow control valve, and the engine or radiator coolant. I chose to go ahead and use super long life coolant made for Toyota vehicles. Unlike the tutorial videos, how to guides, and other resources available, when I removed the hoses and the control valve the coolant from the radiator system did drain and I also drink the rest of it in order to replace. However, the coolant from the inverter did not drain, or at least not all of it.

    The videos and such resources suggested that the inverter could Coolant would also mostly or completely drained, resulting in meeting to completely replace the inverter coolant. I did lose a little inverter coolant so it seemed by checking the reservoir, so I did go ahead and complete the bleeding process for both the radiator and the inverter after replenishing the coolant in both. And the inverter needed about 1/2 to 1 quart maybe not even that much I did not get to measure it precisely. I did bleed the radiator and the inverter separately with hoses as directed in multiple guides, and the coolant temperature seems to be stable between 180 and 190 varying slightly depending on conditions and speed.
    I also purchased the coolant temperature sensor to replace and could not find it on the side of my engine, all of the resources available to show it should be on the top right hand side when looking for a technicality, the driver side of the engine block closest to drive. Since I could not find this, I did not replace the coolant temperature sensor.

    Since having completed those tasks, I have driven the Prius approximately 215 miles and have used slightly more than 1/2 tank of gas the MFT says I’m averaging 27.2 miles per gallon, my OBD two reader says that I am averaging between 35 to 30 miles per gallon again, very depending on driving and spe since having completed those tasks, I have driven the Prius approximately 215 miles and have used slightly more than 1/2 tank of gas MFD says I’m averaging 27.2 miles per gallon, my OBD two reader says that I am averaging between 35 to 30 miles per gallon again, very depending on the driving conditions and speed.

    So, do I trust the MFD, or the OBDII? Also, there have been a few where the check engine light has come on, the little engine symbol, NOT the red triangle! And I have checked the code and pulled P0171, and twice randomly at different times on different days the P0420 catalyst system throttle position sensor code popped up.

    I am now searching as to why these codes are continuing to return. The P0171 (bank 1 too lean) code, and I see on my OBD app the fuel trim averaging .28-.34 them occasionally spiking to .40, I am not sure what to do with this information..

    What aspect should I consider replacing or repairing next? I’m still getting pretty rough mpg. MFD says 27.2, OBD app says 35-38.
    I know that I’ll be doing a manual calculation when I refuel next.

    I’ve included a screen recording of my OBD app displays as well as pics of the MFD and combo meter while driving on the flat interstate with the cruise set at 75mph and AC on recycled at medium speed.

    I’ve only ever run shell fuel since I purchased it, and I do a fuel treatment cleaner LUCAS brand, every other fill up.

    I just want it normal and to get the fantasy45-50 mpg Prius is known for !!
    Thanks again for any advice or tips.
     

    Attached Files:

  16. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
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    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    In your prior posts I did not notice whether you had replaced the iridium spark plugs with the correct NGK or Denso plugs, or replaced the engine air filter. If you had not previously verified the condition of those parts pls do so now.

    Also, clean the mass air flow sensor and make sure there are no leaks downstream from the MAF sensor to the intake manifold. For example the PCV hoses should be inspected.

    Do you reset the MFD mpg counter when you refuel? If you do not reset then the mpg counter will show average mpg since it was last reset.
     
    #16 Patrick Wong, Jun 21, 2019
    Last edited: Jun 21, 2019
    Wville likes this.
  17. Wville

    Wville New Member

    Joined:
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    Vehicle:
    2006 Prius
    Model:
    Base
    Hey there, Thanks for calling that to my attention, and my apologies. Yes, when I purchased the car, the first of the maintenance I completed, was replacing all the spark plugs with the recommended type and the most expensive brand at O'reillys, I know the expensive ones probably work about as well as the cheap ones, but since plugs are replaced so rarely, I thougth it would be a good idea to potentially get a little more life out of them.
    Also, in the same day, I replaced the Engine Air filter, Changed the oil to full synthetic (if it wasn't already, didnt have any records) and the filter, I also changed the cabin air filter. I went back to my first few posts, as I thought I'd included those items, but it appears not... lol However, all of this was done at the time of the initial post along with the other items shown. Thanks again!! lol

    The MFD is reset every time I refuel, and as shown in the images, the MFD does not seem to be accurate either in the realistic "instant" or in the averaging mpg's.

    Prior to replacing the Flow Control Valve this week, about 2-3 weeks ago, I thoroughly cleaned the MAF and the Throttle Body until they were both almost sparkling (With appropraite cleaner).
    I have even contemplated replacing the MAF sensor; however, the OBDII app shows the A/F is normal range. So, I am not sure about if the MAF would allow normal ranges if it were not functioning correctly?

    As far as inspecting the intake and PCV Hoses, I am not entirely sure how I could do that without removing them all and doing what, the cork in the ends, soapy water (bicycle tire trick)? lol

    I read somewhere online that the P0171 code could be a number of things; however, I've slowly checking off the possibility of each them off the list one by one, and honestly seems like I will have rebuilt the entire durn car by the end of it... LOL :)

    I am all game to check the hoses, but I wonder if the hoses were to blame, and intake were an issue if it would not run properly, or even sputter, die, and choke while gs engine was active?
    Thanks again, I look forward to trying out all suggestions lol
     
  18. Wville

    Wville New Member

    Joined:
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    Vehicle:
    2006 Prius
    Model:
    Base
    Update again:
    Hello everyone,
    Alright, so I posted last night while on my way for a short trip, about 120 miles, and when I finished the trip, I had completed 270 miles on that tank of fuel, and refueled at shell, it took 5.424 gallons to fill back up, which according to my calculations is roughly 49.7 MPG. which is AMAZING!! I can totally live with that!! This is what I have been looking forward to!
    However, my question is why do these codes keep returning, almost all of the electrical components have been either checked, rebuilt, or replaced.
    I don't think I mentioned in my post from earlier today/last night, that I had also replaced most of the mini fuses under the hood, and also replaced the 120A Fuse link in the adapter thing that connects to the AUX Battery.

    I really do need to find a thorough detailed walk-through video on where the coolant temperature sensor is located on the GEN 2 prius, I think I may have to dismount the inverter reseroir and some other items just to be able to dig around to find it.

    Last night after making my trip, I did some around town driving 10-15 miles total, with multiple stops. It seems that even though I clear the P0171 code, it continuously comes back every time I get back in the car or turn it off and then turn the car back on. After one of my stops, I cranked the car back up and got these codes shortly after cranking, without even moving the car, which seems bizarre. P0171 (too lean), P0A80 (replace hybrid battery), and P3000 (Battery control system). I cleared the codes, and drove around with a few more stops, and none of the battery codes ever returned, just the P0171.
    Then occaisionally the P1121 (Throttle/Pedal Position Sensor/Coolant flow control valve position sensor circuit stuck) code has popped up randomly, both before and after the flow control replacement. Is it possible I should look into replacing the Throttle/Pedal position sensor?

    I mean if it maintains that kind of actual MPGs, I really don't care what it says... Just curious what is off to continuously throw these codes.

    Short 90 Mile trip home to work overnight tonight, I am going to retop off the fuel, and reset trip/MFD/ etc and see how that goes...

    Thanks again for any help/advice!!!
    Attached are screen shots of the codes.
     

    Attached Files:

  19. cnc97

    cnc97 Senior Member

    Joined:
    Mar 13, 2018
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    1,332
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    Location:
    Evansville, IN
    Vehicle:
    2010 Prius
    Model:
    Three

    On your p0171, does it come back right away when cleared, or does it take a little bit? If it comes back right away, the MAF is bad. If it takes a little bit, check all of the attachment points of the air intake system, as unmetered air could be getting into the engine. Spray the intake manifold and air box while the ICE is running in maintenance mode, the ICE will respond if you hit the leak.
     
  20. Wville

    Wville New Member

    Joined:
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    Location:
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    Vehicle:
    2006 Prius
    Model:
    Base
    The P0171 does not come back immediately when cleared. It typically comes back on only. When the car has been recently cranked, and sometimes a few miles into a trip it’ll come on. Tonight it didn’t come on when I cranked after it sitting most of the day.

    What would you recommend I spray with?
     
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