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Right part to fix P2238?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by BuyJapanese, Jan 27, 2022.

  1. BuyJapanese

    BuyJapanese Member

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    Can anyone confirm this is the right part to fix an intermittent/recurring P2238? Hardly seems worth $170! Maybe if there's a damaged wire or something on the way in I can just replace that instead. The light seems to come on more when the engine is very cold (right after winter start), very hot (after 20+ min running in summer with AC on), or after rain.

    89467-47010 Genuine Toyota Air Fuel Ratio Oxygen Sensor
     
    #1 BuyJapanese, Jan 27, 2022
  2. BuyJapanese

    BuyJapanese Member

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    Also has anybody used any of the aftermarket parts successfully for this A/F sensor? If so what brand?
     
    #2 BuyJapanese, Jan 27, 2022
  3. Tombukt2

    Tombukt2 Senior Member

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    I have cheap aftermarkets on all five of my Toyota's here in the driveway which are not all Priuses at the moment Sienna's corolla's etc I've used Bosch and I've used even cheaper brands that I can't even pronounce sound like some kitchen product or something like that Denso is very expensive A lot of the denso stuff is also made in the US now I think they just closed the plant in South Carolina so whatever you're reasoning these type of sensors generally it's not worth it to pay the high dollar for the denso dealer part I've had boss units that cost $39 that about lasted the vehicle or went to the junkyard when the vehicle did and we're still working so I am not one to be paying a lot of money retail for parts that I don't have to and I don't
     
    #3 Tombukt2, Jan 27, 2022
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    #4 TMR-JWAP, Jan 27, 2022
  5. ChapmanF

    ChapmanF Senior Member

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    Let's see you build one. ;)

    Now you're talking. The sensor you listed does seem to be the right sensor, if the sensor is the problem, but when you look that code up in the repair manual (more info), you do find a half-dozen pages with troubleshooting steps you would follow to rule out wiring issues and such before spending the money on the sensor. So going through the steps can save you $170 if it turns out to be something else (plus save you the aggravation of spending $170, changing the sensor, and finding you still have an issue).
     
    #5 ChapmanF, Jan 27, 2022
  6. SFO

    SFO Senior Member

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    #6 SFO, Jan 27, 2022
  7. BuyJapanese

    BuyJapanese Member

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    Not techstream...just one of those generic $30 ones. I was also sometimes getting P0172. I thought a bad ignition coil might be involved. I replaced spark plugs 3 years/25k ago. Just last week I had P0300 and P0301, which was helpful. I cleaned MAF sensor, regreased ignition coil boots (they were all very dried out) made some notes and swapped coils around. Engine seemed to run smoother, with no obvious misfire, but then the P2238 came back after 100 miles or so. For now I'm just clearing the code and continuing to drive, see how stubborn the code is.
     
    #7 BuyJapanese, Jan 28, 2022
  8. SFO

    SFO Senior Member

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    How many miles on the vehicle, as A/F sensors don't last forever.
    Having techstream may help with the workup for DTC P2238, then you can play with the fuel trims. If you have no interest in throwing parts at the problem, then it would be best to go step by step through the workup.
    Here is the workup for DTC 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/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/2054m/cip0171.pdf
    Did you buy the spark plugs online, as there are plenty of counterfeit parts out there now.
     
    #8 SFO, Jan 28, 2022
  9. BuyJapanese

    BuyJapanese Member

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    335k!

    Yes, these parts from Amazon, they seem legit
     
    #9 BuyJapanese, Jan 28, 2022
  10. ChapmanF

    ChapmanF Senior Member

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    I hope so; the incidence of counterfeiting seems to be out of control.

    With Amazon, it doesn't seem to be necessarily useful even to go by seller reviews and pick a specific seller ... because if they have seller A and seller B who list the "same" item, and you order it "from" seller A, and Amazon sees that they have seller B's stock in a nearer warehouse, it's possible they might just send you that.

    The Automotive Anti-Counterfeiting Council whitepaper linked above kind of tiptoed around the actual name(s) of the "at least one" online marketplace that does that, but I'm pretty sure I've had it happen to me, when I ordered on you-know-where.
     
    #10 ChapmanF, Jan 28, 2022
  11. SFO

    SFO Senior Member

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    If still original at 335k, then just replace the upstream A/F sensor.

    Have you ran some PEA in the gas tank?
    There are a bunch of online resources showing the differences, from images, videos, and websites.

    fake ngk spark plugs at DuckDuckGo

    fake ngk spark plug at DuckDuckGo

    https://www.blingstrom.com/modmondays-fxt-1/2020/1/5/ngk-counterfeit-spark-plugs-how-to-tell-the-difference-ilfr6b-6481

    You could have real NGK platinums, and they may have run through their lifespan at 25k. OEM specs iridium, and those will last 100+k
     
    #11 SFO, Jan 28, 2022
  12. BuyJapanese

    BuyJapanese Member

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    I run a quart of redline before every oil change. I'll pull the plugs, measure gap, etc. next time MIL comes on.
     
    #12 BuyJapanese, Jan 28, 2022
  13. dolj

    dolj Senior Member

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    Don't do that if you have real iridium plugs. You more than likely will damage the iridium tip. However, if you have counterfeit plugs, it should be quite obvious when you look at them. Especially if the gap is way larger than spec after only 25,000 miles.
     
    #13 dolj, Jan 28, 2022
  14. ChapmanF

    ChapmanF Senior Member

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    I'd guess it's safe to measure the gap; what the manual cautions against is trying to change it.
     
    #14 ChapmanF, Jan 29, 2022
  15. SFO

    SFO Senior Member

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    But these may be platinum.
     
    #15 SFO, Jan 29, 2022
  16. BuyJapanese

    BuyJapanese Member

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    I've now had P2238 come back about 4 times every ~100 miles or so. I have the A/F sensor and downstream O2 sensor on the way from rockauto, $176 for both with shipping for Denso parts. I'll track actual mileage between fill-ups for 1000 miles or so before and after I swap them to see if there's a measurable mpg improvement too. I'll do the electrical testing in the repair manual when I'm taking off the old ones, but I'll probably put the new ones in anyway.
     
    #16 BuyJapanese, Feb 7, 2022
    SFO likes this.
  17. BuyJapanese

    BuyJapanese Member

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    Whoof. What an annoying job. I finally got around to replacing both sensors today. I had tried once before, got the windshield wiper motor tray off, and then realized like many before me that I didn't have the right tool because of the A/F sensor's heat shield.

    This 66750B from toolsource is the perfect size and I highly recommend it. Make sure you get the thin-walled part with the "B" in the part name. There's another thin-walled socket on amazon that fits inside the heat shield, but many reviewers have pointed out that it's longer than it needs to be and makes the job even more cramped.

    The service manual calls for removing the inverter. This is not that hard if you've done it before, and I'm sure it makes the job less greasy and cramped, but it also involve more bolts and other parts. For me, I prefer more cramped hands and fewer moved parts.

    Most of the people who do this remove the exhaust manifold heat shield, but this is NOT NECESSARY. The toolsource tool gets past the heat shield just fine, but it gets you less room to work. The hardest part is that there's very little room to move your breaker or cheater bar. I think an 18" flex head ratchet would be the perfect tool for this job, no breaker/cheater needed with those 18 inches, but I don't have one.

    I did end up partially removing my heat shield. I removed the top two bolts and bent it back. That let me attach my ratchet from the other side of the socket. The top two bolts are less likely to break than the bottom two. That put me in this position, pictured, with a 1" extension. This gave me just enough extra room on the ratchet handle (away from all the hoses on the right edge of the pic) to leverage my cheater pipe.

    1F764FA0-C335-4943-A7D4-45525A451B2C_1_105_c.jpeg
     
    #17 BuyJapanese, Mar 11, 2022
  18. BuyJapanese

    BuyJapanese Member

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    Also, over the last ~1500 miles before this change I got and cleared P2238 seven times and averaged 38.1 mpg according to the car. I'll report back on my mpg in the next month or so.
     
    #18 BuyJapanese, Mar 11, 2022
  19. Wischman

    Wischman Junior Member

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    Any updates?
     
    #19 Wischman, Feb 28, 2023
    SFO likes this.
  20. Wischman

    Wischman Junior Member

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    New+1 for the Schley 66750B, not removing the inverter and accessing the O2 sensor from below the car. I tried the tekton socket but it does not fit inside the shield off the sensor only the 66750B does.

    I do all of the work on all of my cars, Took about an hour and a half in total. Cowel goes quick with an electric impact gun, the O2 sensor for 16 years and 182000 mi came off pretty easily, just warm up the engine first so the exhaust pipe expands.

    I had codes p0031 and p2237, this fixed both.
     
    #20 Wischman, Mar 6, 2023
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