Check engine light on, P1116, P1121, P1123 codes

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Fatmatt86, Feb 15, 2020.

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  1. Fatmatt86

    Fatmatt86 Member

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    The check engine light keeps coming on. I have a FIXD device and it keeps showing P1116, P1121, P1123. This happened about 2 months ago, so I looked up the codes here on this forum and purchased a new Coolant Valve, the one with 3 hoses going to it, and made the repair and topped the coolant off, and cleared the codes. Fast forward to this week, and check engine light came back on with the same codes. I'm like I already made the repair, and cleared the codes, but they come right back on the next time I drive the car. I have heat in the cab, works really well, so wondering if the code is valid. It there a way to check the valve. Both too hoses were hot and the bottom hose seemed a little cooler than the other 2. Does this sound faulty. Gonna need to get it inspected next month and would like to get this fixed before taking it in. Prius is a Screenshot_20200215-175010_FIXD.jpg 07 prius
     
  2. ChapmanF

    ChapmanF Senior Member

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    It sounds like you've fallen victim to "fortune-cookie repair", which is where you look at the one-liner fortune cookie that you find next to a trouble code, say it says "coolant valve", so you think "oh that means the repair is to change out the coolant valve" and you do that, and then it's surprising that there's still a trouble code.

    The trouble is, those one-liner fortune cookies are only minor memory jogs for what the code is about; they are not enough by themselves for you to know what the car is telling you. That information is in the Repair Manual (more info), where you will find that each of those codes has a section detailing how you would troubleshoot that problem. A very important piece of information for each code is printed in a box at the start of its section: it's called the "detecting condition", and it tells you exactly what the car had to see happen for that code to be set.

    For example, the P1116 tells you that the car's computer distrusts the reading it is getting from the outlet temperature sensor of the coolant thermos, either because it doesn't see the reading change enough during the cycle where it pumps hot engine coolant into the tank, or because at the end of that cycle there's still too big a difference between that temperature reading and the one from the engine temperature sensor.

    P1121 tells you the car's computer distrusts the signal it's getting from the coolant valve position sensor, either because the position doesn't appear to change when commanded, or it does but there isn't the expected effect on the outlet temperature reading (hmm).

    P1123 says the coolant valve position signal was out-of-range high for two seconds or more, and the computer would have responded by saying "I can't get valve position, so I quit trying to move the valve at all."

    While I was writing this, after the first two codes I was thinking more likely something to do with the outlet temperature and the valve position feedback was ok. That could happen, say, if the outlet temp sensor were bad, or its wiring or a connector, or there's a clog in the coolant recovery plumbing somewhere so hot coolant really isn't getting pumped in as fast.

    But then there was that third code, which makes it look more likely that there is maybe a wiring problem to the coolant valve position sensor, like the position wire has some insulation damage and is bouncing against something higher than 4.8 volts, or the ground connection for the sensor is open. The manual says the computer will give up moving the valve when it sees that, and leave it in whatever position it was, so in that way the outlet-temperature questions would still be explained.

    So as you can see, when a computer in a car gives some trouble codes, there is still work left for the human to do to figure out what's the reality on the ground that made the computer set those codes. The computer itself is stuck inside a box and can't go out poking at parts with flashlights and multimeters, so it can only tell you things it saw from inside its box, and hope you will be able to find out why it saw those things. (That's still a big head start compared to if you had no trouble codes and only knew something was wrong with the car.)

    For troubleshooting, I would probably start with the six pages of check-it-out steps in the Repair Manual for the P1123 code. I'm thinking the P1116 and P1121 might be resolved when that problem is found and fixed.

    Chances are, finding and fixing that would have solved the complete problem even without replacing the valve as you did, but given the new one is in there now, there's probably no reason to change it back; you can't return it once it's been put in service.

    You might want to ask the mods to move this thread to the Gen 2 forum, if you have a 2007.
     
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  3. bisco

    bisco cookie crumbler

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    How many miles on her?
     
  4. SFO

    SFO Senior Member

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  5. ChapmanF

    ChapmanF Senior Member

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    • SFO and Fatmatt86 are the same person
    • Fort Worth is now in northern California (side effect of relocating Kansas City?)
    • SFO operates long-range odometer-reading drones
     
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  6. Raytheeagle

    Raytheeagle Senior Member

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    Wasn't that in the Gen3 he has :whistle:?

    This is supposedly on a Gen 2 (2007) in post 1;).

    But maybe @SFO is moonlighting(y).
     
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  7. SFO

    SFO Senior Member

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    Doh. Sunday coffee isn't pumping on all circuits. Might need to brew the light roast next :eek:
     
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  8. Raytheeagle

    Raytheeagle Senior Member

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    Could've been me as we are traveling in Spain and I'm just checking when I have WiFi ;).

    Plenty of good wine and salty meats along with historic viewings (y).
     
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  9. SFO

    SFO Senior Member

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    Sounds like @Fatmatt86 has a multigenerational fleet :coffee:
     
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  10. Raytheeagle

    Raytheeagle Senior Member

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    Yes you do:p.

    That is, if @ChapmanF is right:censored:.
     
  11. SFO

    SFO Senior Member

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    Actually did look at a lower mileage gen2 yesterday, though hard to justify such when you can only drive one at a time.

    Not sure if @Fatmatt86 has any additional vehicles, as the drones are only reporting the one known oil burner.

    The most recent drone foray has now reported the correct mileage as 272,016
     
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  12. Raytheeagle

    Raytheeagle Senior Member

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    Going back to your roots:whistle:?

    Or have you parted ways with the gen3 we cleaned the egr circuit on:unsure:?

    I know your heart is with the gen2;).

    So tough to resist(y).
     
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  13. Fatmatt86

    Fatmatt86 Member

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  14. Fatmatt86

    Fatmatt86 Member

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    Haha. I mentioned it in another post about oil consumption just last night.
     
  15. Fatmatt86

    Fatmatt86 Member

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    Okay, so I've checked every single fuse and relay and it still comes on every 2nd time I start the car after clearing the code.
     
  16. ChapmanF

    ChapmanF Senior Member

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    I'll stick with my story from #2; the workup for P1123 is where I would be inclined to start.
     
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  17. SFO

    SFO Senior Member

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    Trying, but the gen3 is still acting like a gen2 tank. Can't get it to die, even with the failed HG :confused:
    Keep thinking about dumping it, but the seat warmers are effective this time of the year :D
    The gen2 has some pluses for sure. Would go newer, but after what Toyota did to the gen4, I'll wait and see how ugly the gen5 is.
    Yeah, the price is right and it only needs a battery or two o_O
     
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  18. Black2006

    Black2006 Member

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    I get an intermittent engine warning light on a 2006 Prius that generally runs perfectly. It first came on last year and it basically disabled the car (breaks felt like manual, all lights on, etc.). I took it in and they replaced the coolant pump (I believe, if I remember right).

    But it came back on a month ago and I took it back in, they checked it and said it was a code DTC P1116, but it was a fluke, so they reset it and sent me on my way. But as I was coming up a steep hill, the light came back on. It disappeared again after a couple of days, then came on for a few hours and disappeared again.

    It may be a coincidence, but the light seems to come on when I have driven at higher speeds, and then go up a hill.

    I purchased a BAFX OBDII reader and the Torq app show one code: POA93 (Inverter "A" Cooling System Performance).

    I am wondering if I should take the car back in (don't really want to do this), or if I can check something relatively easily, or if I should just ignore it? The engine light is not on currently.
     
  19. bisco

    bisco cookie crumbler

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    perhaps they didn't get all the air out
     
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