Check engine (P261B) intermittent

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by TheGreenMonster, Aug 1, 2025.

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  1. TheGreenMonster

    TheGreenMonster Junior Member

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    2003 Prius
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    We've got a 2015 Prius just shy of 100K. A few weeks ago, we were just out of Houston on our way back to Austin when the check engine light came on. We pulled into Costco and filled up the tank while we figured out what to do (the tank was half full already) and when we started the car again, no light. This happened again on last Sunday; my husband decided again to fill the tank (it was about two-thirds full) and once again it turned off as soon as he filled the tank.

    So, this week, although the light is off, he got an OBDII and the code is P261B, water pump. Later he found our much older OBDII, but it just says "error" (no code).

    I think it was our old Gen I, or maybe the old 2003 Camry we used to have, that would sometimes throw a check engine light that would be cleared just by removing the gas cap and screwing it back on, so I assumed this was a similar issue, at least until the OBDII indicated the water pump.

    We always click the gas cap a few times when we put it on, and never ever top off the tank when filling up. The last maintenance was at the dealer last October, I think the battery was replaced and brake fluid on top of the usual. Even though it's getting up there in age the car has been extremely reliable.
     
    #1 TheGreenMonster, Aug 1, 2025
  2. NutzAboutBolts

    NutzAboutBolts Senior Member

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    Replace the water pump with an Aisin brand, it’s probably on its way out.
     
    #2 NutzAboutBolts, Aug 3, 2025
    Brian1954 likes this.
  3. tweedle99

    tweedle99 Member

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    III
    I've seen ppl posting about just changing out the impeller since that's the only moving parts. I've seen it on amzn. $20 ish vs 2-300

    When mine failed, the impeller plastic covering was cracked which made it swelled up and start rubbing on the housing.
     
    #3 tweedle99, Aug 7, 2025
  4. NutzAboutBolts

    NutzAboutBolts Senior Member

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    looks cheap… the wp I bought was 155$, it’s not going to break my bank so I’ll stick with it. I’m not sure how long the impeller parts would last and it’s aftermarket. Can’t tell if it’s from Aisin or not. But if it works for you, go at it (y)
     
    #4 NutzAboutBolts, Aug 7, 2025
  5. tweedle99

    tweedle99 Member

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    Just a suggestion, in case due to budget.

    The replacement impeller was not around when i swapped out my WP about 5 yrs ago. I did buy one as a "spare" Dont want to spend too much $$ on 15 years old car w/ 215k miles
     
    #5 tweedle99, Aug 8, 2025
  6. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Vehicle:
    2010 Prius
    Model:
    Touring
    Being in Canada, US sources can be sketchy, and I’ve found Amayama a reliable source. Google:

    Amayama Aisin WPT-190

    and see what they’re asking. For me it amounted to $130~ USD, all-in with shipping. So far they’ve never charged me extra, say for sales tax or import duties.

    link:

    https://www.amayama.com/en/part/aisin/wpt190

    and yeah, good to replace every 100k miles, lots of failures reported here, around 150k.

    Impeller-only replacement is intriguing too. It’d be good to get some verification as to source and reliability. By the time I get to 100k miles that will hopefully have happened. If I ever get there lol.
     
    #6 Mendel Leisk, Aug 9, 2025
  7. tweedle99

    tweedle99 Member

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    The impeller for our cars is similar to them powerhead/pumps in the aquarium hobby. The pump motor is epoxied seal and rarely failed and impeller is the only moving part. Usually when pump failed or failing, I used to just swap out the impeller and back in business.
     
    #7 tweedle99, Aug 9, 2025
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