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Prius dies after changing spark plugs

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Daniel Hanchett, Apr 24, 2022.

  1. Daniel Hanchett

    Daniel Hanchett Junior Member

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    I changed plugs on my 2008 Prius, 265,000 miles, with new Denso plugs. Car was running fine, but check Engine light was on and read occasional misfire. Car started up and ran for a few seconds after changing plugs, then died with the red triangle. I believe this was the first plug change. Don’t know what codes are showing up now, I live in rural Michigan. Thanks for any suggestions.
     
  2. mr_guy_mann

    mr_guy_mann Senior Member

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    Where did you get the spark plugs? ebay and amazon are known for counterfeit items (like plugs). I think that your car is only trying to start but never running. The prius spins the engine at 1000 rpm when it wants to start- if it doesn't run it will stop after 8-10 seconds (sounds like a start and stall but is really never started at all).

    A possibility for your problem is that something is wrong with a coil- each coil should send a signal to the ECM that it produced a spark when commanded. If any coil is faulty or not plugged in and doesn't send the signal, then the ECM can disable the engine. BUT that's a guess.

    You really need to have any and all codes read from (all) ecu's in the car. (and don't attempt to start the car more than a couple times unless you find and correct a fault. Each start attempt uses power from the HV battery- don't want to run that down too far).
     
  3. Another

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    Coils, plugs and cables. Did you crack a cable?
     
  4. Daniel Hanchett

    Daniel Hanchett Junior Member

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    I did get the plugs from Amazon, paid about $32 for the 4 of them. A couple times it did start and really chugged, but the other times it sounded fine, it probably was just spinning the engine, I didn’t know it would do that. I did try to start it quite a few times. Maybe I damaged one of the coils, the one on the right was pretty bent in there. How can I tell if the plugs are counterfeit? I try to find a way to get the codes read today. Thanks so much for getting back with me.
     
  5. ChapmanF

    ChapmanF Senior Member

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    What cables do you have in mind?
     
  6. TMR-JWAP

    TMR-JWAP Senior Member

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    What spark plugs did you install? Brand, model and source?
    Did you reconnect the wire harness to the coils?
    Did you disconnect the 12v battery prior to performing this job? If so it may be possible you're running into a problem due to ECU going back to default values.
     
  7. Daniel Hanchett

    Daniel Hanchett Junior Member

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    I used Denso SK16R11, bought on Amazon for about $32. I did reconnect the the wire harness. I did not disconnect the battery before installing, but have disconnected it several times since to clear the red triangle code. The boxes the plugs came in looked legitimate. What can I do about the possible ECU default? Thanks so much for your response.
     
  8. Another

    Another Senior Member

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    Spark plug wires
     
  9. ChapmanF

    ChapmanF Senior Member

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    Aren't any
     
  10. Another

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    Is to there a harness?
     
  11. ChapmanF

    ChapmanF Senior Member

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    The coils have 12 V supply connections, just like in any other car. Nothing replaceable (without replacing or rebuilding the whole engine wire harness).

    Because the coils sit right on top of the plugs, there are no "spark plug wires" like what you might replace in other cars.
     
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  12. Another

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    Thanks for the explanation. Your experience is always welcome.
     
  13. Another

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  14. TMR-JWAP

    TMR-JWAP Senior Member

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    ECU default issue. Sometimes happens. Not frequently, but often enough that I've experienced it a few times. When you drive your car, there are some parameters the ecu learns ands adjusts while driving. These change over the course of miles and years. Things like throttle body position due to carbon buildup. It may not seem like much, but when the 12v system is turned off, and the ecu goes back to default, the learned value is gone and is now the "as new" value. If different enough from the learned value, the car may not start. I've been able to resolve this each time by thoroughly scrubbing the interior of the throttle body to remove the carbon deposits, allowing the throttle plate to return to it's 'as new' position, which now matches the 'as new' default value. It's also a good time to remove and clean your mass air flow sensor, especially since removing it gives you much better access for scrubbing the inside of the TB. I remove the air cleaner assembly, remove the MAF sensor (unplug it, then remove the screws just using finger power and a phillips screw driver tip), scrub the TB with a small toothbrush and TB cleaner, while holding plate open with a tool. On the MAF, clean the exposed temperature bulb (you'll likely be amazed at the difference) and the element that is buried inside the housing using MAF cleaner. The element inside the housing is delicate, but I've gently used a cotton swab to brush it after spraying and was surprised at how much additional stuff came off. I had to do the cotton swap thing because after cleaning the first time only with spray, I continued to get random lean codes. problem solved after the cotton swab.
    Don't forget to plug the MAF harness back in after you're done. I also ALWAYS disconnect the 12v battery before I work on/disconnect any sensors.

    This little default issue is one reason why I stopped disconnecting the 12v battery when replacing an HV battery. Hate it when someone freaks when their car wont start/run and codes out after a HV battery replacement. Then I end up spending 15 minutes explaining, and more time disassembling and cleaning. Easier to just leave it connected....and a good reason to use a 'saver system' when replacing a 12v battery.
     
  15. Daniel Hanchett

    Daniel Hanchett Junior Member

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    Installed new 12V, shows 11.8 on screen. Tried battery in older Prius I have and it worked. Tried jumping with different vehicle and showed 12.9. Still no ready light. Brake lights working. No codes showing up yet on Tonwon pro Bluetooth. Switched plugs back, no different. Don’t know if HV battery is too low.
     
  16. Daniel Hanchett

    Daniel Hanchett Junior Member

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    Also cleaned MAF and TB, reconnected the battery. Will not go into ready mode. The 12V now reads 11.5V. Brand new battery, took it back in to a different store, they said battery checks good. Still no codes, does the engine have to start to show codes? Thanks again for any advice.
     
  17. dolj

    dolj Senior Member

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    So have you cleaned the MAF sensor, throttle body and throttle plate as advised by TMR-JWAP in post #14? If you haven't that should really be your next priority.

    What is the voltage reading of your hybrid vehicle (HV) battery, out of interest?

    BTW, not that it is likely anything to do with your current problem but as a general 12 V battery housekeeping issue,11.8 V for a new 12 V battery is pretty poor. Get that charged up using an external smart battery charger if you care at all about the longevity of it. Is it an AGM battery or a standard flooded one?
     
  18. mr_guy_mann

    mr_guy_mann Senior Member

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    What app are you using with your OBD bluetooth adapter? Does the dash - speedo light up (and all the warning light test) when you try to ready up? If it does but no ready then there has to be a code somewhere. Dr Prius app might help for hybrid control (and HV battery codes- maybe).

    There's a sticky at the top of the Gen2 Technical forum about apps- short form is the Autel Maxi AP200 is pretty much the best device and app for diagnostics.

    You have to go to Techstream or a similar level professional scanner to have more functionality.

    Posted via the PriusChat mobile app.
     
  19. Daniel Hanchett

    Daniel Hanchett Junior Member

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    Auto Doctor app, I couldn’t get Dr Prius to cink up to my adapter. Everything seems to light up except red triangle. I’m not sure how to get the voltage reading of the HV battery. The new 12V battery is just a standard Auto Valve Prius battery. I’ll have to get a better device and app as you suggest, because nothing shows up on this one. I did clean the TB and MAF sensor. Thanks for your posts, I’m kind of overwhelmed with this whole situation, never had much luck working on my own cars.
     
  20. Another

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    Dr Prius even free version will get you HV battery parameters
    Look on their website for the guidance on dongle that is compatible. Should be about $25 on Amazon