Intake Manifold Wire Harness help

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by RavenPri, Nov 2, 2025 at 6:24 PM.

  1. RavenPri

    RavenPri New Member

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    Vehicle:
    2012 Prius
    Model:
    Two

    So I set out on an adventure to flush the coolant, clean the EGR and intake manifold as its been long overdue. Of course every hose and wire harness were on tighter than heck. The last harness I needed to remove of course broke! And yes I was careful as I could be for 10 minutes trying to get it off. Even after it broke it took a lot of pulling with some needle nose pliers to get it off. Anyway, I was able to get the part in stock and now need to splice it back in.

    Unfortunately I am not sure which side is goes to which now (goes for putting everything back together :(). I checked with a volt meter and the positive number is the purple wire touching the black probe and the negative number displays when the red probe touches purple. Of course pending if the probes are in correctly (n).

    I tried and still trying to find a wire diagram, but probably would have difficulties figuring how to read it. So I am looking for some help on which is the correct way the harness gets wired up. I am lead to believe it is officially called 'Canister Purge Solenoid Connector' and it connects to the intake manifold. The purple wire is on the top during testing in case its hard to distinguish, black on bottom .

    My car is my only source of income so I need to get this back up and running soon.

    Thanks,
    2012 Prius Two
    186k miles
    106k last 3.25yrs

    The back story if interested.
    Besides the overdue EGR & intake manifold cleaning and coolant flush, I recently had picked up some engine trouble. It sounded like the car was choking for air or out of gas when the motor would kick in or start to drive off after parked. Some troubleshooting online led me to the "death rattle". o_O oh no not good news. I read that it could be caused by a dirty intake and/or EGR. Ok great that was long overdue, the videos don't look that hard but not easy by any means. Finally figured out how to connect Torque Pro (just needed it set in the app settings :confused:) and got a P0302 error code. Ok well the EGR still needs to be cleaned and it ends up its pretty clogged. Still have it in the ultrasonic cleaner, it seems to be really gunked up. Hopefully not need a new one after all this.

    Anywho, back to the error code misfire cylinder 2, which I was advised to swap the coil and see if it still is # 2 or if it changes then the coil needs to be replaced. But have yet to diagnose that, but first the cleaning. Then I end up reading a post on Reddit that in scenarios like this what happens is the water pump can fail the coolant can dry up inside the radiator and causes head gasket problems and needs to be replaced or a new motor :eek:. Very bad news. I should replace the water pump while got everything apart but its a bit out of budget, but will if I have to.

    Right when the problem chug first happened I checked the oil and it was fine but the engine coolant reservoir was really low, so I topped it off, and after that remained stable but the rattle chug still happened. Tried a couple bottles of fuel injector cleaner and lessened the chug but didn't remedy it. So when I drained the radiator there seemed to be a bit of oil slick on the top. Maybe it is the residue from the new drain tub and when I flushed with distilled water (let it soak in for a bit, engine cold not running) there still appeared to have a little oily sheen on top. I still want to engine run flush and we'll see if there is still any oil slick. Have been getting oil sampled through Blackstone and the tests (4-5 8.5k~12k intervals after a hand full at 5k) have all been clean and received a big thumbs up from the lab. So I know water isn't getting into the oil.

    After all that is when I read the Reddit post, it felt like I'm in the exact same scenario :cry::cry:. I really hope its not and it will be all sorted once everything is snaped back together. :unsure:

    If you got this far thank you for your time and the main problem right now is getting the wire harness back right.

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  2. Iketorz

    Iketorz Junior Member

    Joined:
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    Location:
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    Vehicle:
    2010 Prius
    Model:
    IV
    Not sure if you're asking more than this but purple is toward the back and black is toward the front.
     
  3. RavenPri

    RavenPri New Member

    Joined:
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    Location:
    North West California
    Vehicle:
    2012 Prius
    Model:
    Two
    Thank you that is very helpful! I tried looking at my friends '13 but couldn't see anything without taking the airbox off.
    :barefoot: crossing fingers
     
  4. Mendel Leisk

    Mendel Leisk MMX GEN III

    Joined:
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    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    The head gasket is likely failing, leaking coolant into cylinder two. Borescope inspection can confirm.

    You’re correct that EGR cleaning is long overdue. It’s my conviction that protracted running of the engine with the EGR system ineffective due to carbon clogging is what’s causing the head gasket failures.

    it’s always good to get on the EGR cleaning, but don’t kid yourself, deal with the head gasket first.

    More info on EGR cleaning and head gasket linked in my signature. Last link is full engine section from repair manual.

    (on a phone turn it landscape to see signatures)