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Got fault code P3191 on my 2002 Prius...

Discussion in 'Generation 1 Prius Discussion' started by War_Destroyer, Dec 13, 2022.

  1. War_Destroyer

    War_Destroyer Junior Member

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    Hi guys, this morning I started the car and got an exclamation point icon. When I scanned it with my cheap Bluetooth scanner I pulled the following fault code P3191. I decided not to use the car at that point, what does the code mean in terms of a 1st Gen Prius? Is there a common fault? The last time I got an exclamation point warning it was over the summer, but it was related to heat with temps in the summer sometimes reaching 110F. Today is definitely one of the coldest days of the year with its being in the 40s F, I doubt it's that simple!

    20221213_104313.jpg Screenshot_20221213_104532_Torque.jpg
     
    #1 War_Destroyer, Dec 13, 2022
  2. Trombone

    Trombone Member

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    Check out this thread: 2002 Prius DTC Code P3191 | PriusChat
    Could be your problem is as simple as an MAFsensor cleanout. I did this on my '02 and that cleared up the problem. See the last post in the cited thread.
     
    #2 Trombone, Dec 13, 2022
  3. ChapmanF

    ChapmanF Senior Member

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    Your scan tool only shows "powertrain" because P3 codes are not standardized across all car make and models the way P0 codes are.

    [​IMG]

    So the tool is effectively saying "well, I know it's some powertrain code because of the P, but beyond that, you'd have to look in the right repair manual for your car model to see what it means." (That's a good way for your scan tool to behave. Some of them would just show you a random fortune cookie for what P3191 means in some completely different car, and send you down the wrong track.)

    In a Prius, P3191 just means the engine isn't starting; the car cranks it and cranks it with MG1, but it never started producing more power than MG1 was putting in.

    So that isn't the kind of code that is pinpoint on any one particular cause. As with any gasoline engine that isn't starting, there are the usual suspects to check, and you just have to go through those.
     
    #3 ChapmanF, Dec 13, 2022
  4. War_Destroyer

    War_Destroyer Junior Member

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    The car did start right up though, no struggle at all... I took a different car to work but my bro says that it does start right up, that the exclamation warning disappeared, and drives well around the block. He says the fault still posts as current, not sure if that'll change, but I'll buy some MAF cleaner after and give it a good cleaning. Do I clear the code after I do?
     
    #4 War_Destroyer, Dec 13, 2022
  5. ChapmanF

    ChapmanF Senior Member

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    Because MG1 cranks the engine for starting at the same RPM as a normally-running engine, rather than wheezing away at 200 RPM or so like a traditional starter, a Prius always sounds like it "starts right up" even before the engine has actually started. It will also happily drive away on battery power, while still trying to crank and start the engine.

    When my Gen 1 was getting old and a bit balky to start in cold weather, it would usually "start right up" and take me about three blocks from home on battery power before finally giving up and posting the P3191 code.
     
    #5 ChapmanF, Dec 13, 2022
  6. War_Destroyer

    War_Destroyer Junior Member

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    Oh wow, so what would be the proper way to know that the gasoline engine is up and running and not the electric motor making it seem like it is? Wouldn't that just be taking up to speed? Anyway, I just bought a MAF sensor cleaner for $5, can't wait to see the result. Cleaning the MAF sensor has worked as a solution more than once on my old Mercedes vehicles lol
     
    #6 War_Destroyer, Dec 13, 2022
  7. ChapmanF

    ChapmanF Senior Member

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    It all normally works so well, you don't have to care. :)

    If it stops working that well, a little engine TLC might be in order, and then it'll be back to working so well you don't have to care.
     
    #7 ChapmanF, Dec 13, 2022
  8. Tryyn

    Tryyn Junior Member

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    Try to rev the engine by pushing the accelerator (briefly) to the floor with the transmission in park. If the engine is running, it will rev up to about 2500 RPM. If MG1 is cranking the engine, the engine sound/RPM will stay constant.
     
    #8 Tryyn, Dec 15, 2022
  9. War_Destroyer

    War_Destroyer Junior Member

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    Hey guys, so back on December 13th I cleaned the MAF sensor REALLY WELL as well as the sensor and harness connectors with MAF and connector spray cleaners, and cleared the fault.

    I've driven the car far and wide these passed three weeks, but the code (P3191) has appeared once again this morning...One would not know something was wrong without the code, I've used it every day for work going up and down the freeway without a hiccup. I drive the Prius a bit aggressively it's not like I'm trying to hypermile it, the engine runs well lol

    What do you guys recommend I do next? The car only has 67000 miles on it and is in pristine condition. It's due for an oil and oil filter change, which I have, and I also bought new spark plugs since it probably still has the original ones, but I doubt this will solve whatever is tripping this P3191 fault code right?

    Edit: I've been using a cheap $10 bluetooth scanner, is there a recommended scanning device for Prius, and for my 2002 model in particular? For example, I have an expensive scanner for my older Mercedes-Benz that doesn't use the OBD port.
     
    #9 War_Destroyer, Dec 30, 2022
    Last edited: Dec 30, 2022
  10. ChapmanF

    ChapmanF Senior Member

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    For scanning the Prius, the OBD port is the only game in town.

    With a good enough scanner, you can look at, besides the P3191 code, various measurements of how the engine's been running. That can help focus things, because the P3191 code by itself only means "hey, the engine produced really lousy power this time when I was trying to start it", so it leaves plenty for the human to figure out.
     
    #10 ChapmanF, Dec 30, 2022
  11. War_Destroyer

    War_Destroyer Junior Member

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    2002 Prius
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    ----USA----
    Could the cold weather be a cause for the P3191 code? Overnight temperature have been in the 35-45F range with the condensation outside the car being frozen on some mornings. The car drives fine and the warning disappears on it's own. I've cleaned the MAF sensor as mentioned before, replaced the sparkplugs, engine air filter, oil and oil filter. I hope it is not some Prius specific module or something that's starting to bug out?
     
    #11 War_Destroyer, Jan 20, 2023
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