P0137 + p0138 after replacing cat

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by k1ngn0thing, Jul 3, 2021.

  1. k1ngn0thing

    k1ngn0thing Member

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    Replaced the downstream o2 sensor before putting in the new cat, and these codes only came up after replacing the cat, so I don't think the sensor is malfunctioning. Left the old exhaust gasket up front and that seems to be the only likely candidate. Are these difficult to replace? I already have the oem part. Does it weld over time from the heat, and would that make the old one tricky to remove by hand? Also, I assume a p0420 code would not go off until this is remedied?
     

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  2. ChapmanF

    ChapmanF Senior Member

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    Have you looked up what the detection conditions are for P0137 and P0138? Those are two I don't have memorized....
     
  3. SFO

    SFO Senior Member

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    How many miles on the vehicle, and have you ever replaced the upstream sensor?
    Which brand did you purchase for the new downstream sensor?
    The two bolts connecting the cat with the exhaust manifold can get pretty tight, you may need an impact gun or breaker bar. If you didn't remove the bolts during the cat replacement then that gasket could be fine, otherwise it should easily pop out after unbolting.

    Here is the workup for DTCs P0136 P0137 P0138 :

    https://share.qclt.com/丰田普瑞斯原厂英文手册pdf格式/Prius Service Manuals 2004/修理手册/04pruisr/05/2054m/cip0136.pdf
     
  4. k1ngn0thing

    k1ngn0thing Member

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    About 268k, haven't personally replaced upstream o2, I got it at 220k. Replacement is a cheap Chinese sensor, got both up and down for 70 bucks total. I don't think it's either sensor as these codes just came on after swappint the cat and resonator so it seems most likely to be the gasket as a leak will throw both high and low voltage codes.
     
  5. SFO

    SFO Senior Member

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    Most aftermarket sensors return poor results, you may need to try the Denso or OEM option.

    Still curious if @PriusCamper had any luck with his aftermarket sensor experiment?
     
  6. PriusCamper

    PriusCamper Senior Member

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    yeah... I bought one for $16 on ebay last Spring and still haven't got around to testing it yet... Will make sure to follow up on this soon.
     
  7. mr_guy_mann

    mr_guy_mann Senior Member

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    I don't hate myself enough to use cheap AM sensors on my cars. The time I have wasted over the years on new bad parts outweighs any "savings" in $$. OE or Denso is the way to go.

    Posted via the PriusChat mobile app.
     
    #7 mr_guy_mann, Jul 3, 2021
    Last edited: Jul 3, 2021
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