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Downstream O2 sensor wires cut

Discussion in 'Gen 2 Prius Technical Discussion' started by Adam W, Jul 2, 2022.

  1. Adam W

    Adam W New Member

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    My wires were cut and spliced together for an aftermarket downstream O2 sensor where it connects to the plug inside my floorboard.

    I want to replace the sensor with a Denso but thinking I need to repair the wiring harness before I can plug it in. Looks like just one wire got removed the plastic connector. Any advice on how to fix this?

    439442DB-7856-4457-BA22-D35B163CBADB.jpeg
     
    #1 Adam W, Jul 2, 2022
  2. jerrymildred

    jerrymildred Senior Member

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    It looks like the wire from the connector to the sensor somehow got severed and someone cut the brown wire before the plug and bunged it together rather than just bung the gray wire back together -- or do a proper wire repair. That was a dumb move.

    Obviously, replacing the harness is not worth the expense. I'm not sure what kind of connector pins that plug takes, but that's one possibility if you want to try to research it. Assuming they are not epoxied in place. I've replaced a few O2 sensors, but never took the time to examine the plugs.

    If that doesn't work out, I'd probably put bullet connectors on the ends of the wires that are affected. Maybe solder an extension on that brown wire first.
     
    #2 jerrymildred, Jul 2, 2022
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  3. Adam W

    Adam W New Member

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    They cut the wire to make the aftermarket O2 sensor work. Assuming the plug config on the sensor wasn’t right. Now I just want to replace the whole downstream sensor (got the dreaded P0420 code) without having to chop wires again. Pretty bummed when I saw this. Not sure if I can pry the connector apart and put the brown wire back in. Maybe best move will be figuring out which wire on the new sensor corresponds with the brown one and splicing it together. I’m ordering a Denso downstream O2 sensor for my 08 Prius.
     
    #3 Adam W, Jul 2, 2022
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  4. PriusCamper

    PriusCamper Senior Member

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    You can get a spare plug at junk yard and wire it in...
     
    #4 PriusCamper, Jul 3, 2022
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  5. jerrymildred

    jerrymildred Senior Member

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    There ya go! (y)
     
    #5 jerrymildred, Jul 3, 2022
  6. Tombukt2

    Tombukt2 Senior Member

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    One of the Bosch O2 sensors I used to buy comes with this plug in the system and you can move the pins around and everything I can't remember the name there was a catchy name for the sensor multi-fit or something like that but it was for Toyota and they also I think had a repair kit for the plug in the car The insta-fit sensor let you remove that plug and have this connector that wired to the wire sitting in your car that you just finished cutting or that were damaged.
     
    #6 Tombukt2, Jul 3, 2022
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  7. ydpplqbd

    ydpplqbd Active Member

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    Is it Bosch Smartlink. See:
     
    #7 ydpplqbd, Jul 3, 2022
  8. Tombukt2

    Tombukt2 Senior Member

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    Yes this is the newest version
     
    #8 Tombukt2, Jul 3, 2022
  9. Adam W

    Adam W New Member

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    That’s pretty sweet but my issue is with the wiring connector that is not on the O2 sensor. It’s the one that clips into a new sensor. I want to buy a Denso but worried it won’t work because the brown wire has been removed.
     
    #9 Adam W, Jul 3, 2022
  10. Tombukt2

    Tombukt2 Senior Member

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    This replaces those pieces . The Bosch works fine in all mine so far . I usually do the upper too . I'm by the direct fit for that because no one can reach up there and cut that one it's right there in between the inverter and back of the engine . So I buy the one that just plugs directly into that gray plug The one down lower that usually cut and fubar I use the one pictured in post it replacee the complete plug assy.
     
    #10 Tombukt2, Jul 3, 2022
  11. Adam W

    Adam W New Member

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    I watched the video and it showed cutting the wire and using the insta-link to hook it up the old O2 connection. If you look at the pic I uploaded, one wire (brown) running from the connector inside the console area was cut.

    What happened is some dude replaced my O2 sensor and the connector didn’t fit so he cut wires on both connectors inside the floorboard/console. When that O2 failed he got another one with proper connections but had to splice together the new one since he already had cut the connector that it would have plugged into.

    Sorry, for all the replies, maybe I’m just confused and not understanding.

    B2FF658D-9F31-45D9-9ADD-8D67903BE92C.jpeg
     
    #11 Adam W, Jul 3, 2022
  12. jerrymildred

    jerrymildred Senior Member

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    So do what @PriusCamper recommended in post #4. Go to a junkyard and cut off the plug from the harness on a junker, leaving enough wire to work with. Then cut off your plug from your harness and solder the wires together. Then you will have an undamaged, functional, factory stock plug on the car that will be ready to receive the plug on the new sensor.
     
    #12 jerrymildred, Jul 4, 2022
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  13. Adam W

    Adam W New Member

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    Update … I crimped the wires with quick connectors and my check engine light went off for about 250 miles. That’s a lot better than the 30 mile off and on rotation I was experiencing. Gives me hope it may be my downstream O2 sensor. I have no idea what brand was installed but read a Denso is my best bet for an affordable and reliable aftermarket sensor.

    Any thoughts on wiring causing faulty readings and an aftermarket O2?
     
    #13 Adam W, Jul 24, 2022
  14. Tombukt2

    Tombukt2 Senior Member

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    You working on upper or lower? Replace the other too. Don't matter if they're cheap just make sure they're the right numbers and put them in the right place on the car.
     
    #14 Tombukt2, Jul 24, 2022
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