How to pass smog test without EGR cooler

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by anonymous, Jul 27, 2018.

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  1. anonymous

    anonymous Member

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    NOTE: This may not work if they look under the hood!!

    If you're like us, you've recently got P0401 somewhere near 200k miles, but were lazy to repair it until suddenly it's time to renew your registration but you've failed the smog test because of the P0401, so you get a 10-day movement permit to repair it.

    But by now, the EGR cooler is completely clogged and will probably take a long time to clean it.

    So in the meantime you need to be able to drive the vehicle.

    To do that, first you need to hook all the coolant lines together with some plumbing parts. For the larger hoses, you can use 5/8" or 3/4" barb fittings; 5/8" will slide right in and rely on the hose clamp to seal, while 3/4" will stretch the tube and will be a little difficult pushing on completely, but will make a good seal. For the small hose, 3/8" fits perfectly. Parts should be metal, preferably brass.

    Then you need to block both sides of the missing EGR loop: the hole in the intake manifold, and the pipe connected to the exhaust manifold. The intake can be plugged with a piece of sheet metal. For the exhaust pipe, a block of wood and a couple of small C clamps works nicely.

    With the hole in the intake manifold, the engine will run poorly and unpredicably as the system struggles to control the throttle with the massive intake leak. And with the opening to the exhaust manifold, your Prius will sound like a smelly motorcycle. or chainsaw.

    You will not get very far before the “CHECK HYBRID SYSTEM” warning comes up. Then soon after that, a bunch of more lights come on and you'll be forced to pull over. The system will refuse to drive until you cover the intake hole with some electrical tape. Then it'll work properly so you can drive back home to make a better intake plug using a pickle jar lid and the EGR pipe to clamp it down.

    At that point you can drive the vehicle… if you want to be poisoned by exhaust fumes… you'll need to set the climate control to loop mode (and perhaps use the filter button cause i've heard the loop mode still lets some outside air in) and/or will have to keep the windows open. So you really should block the exhaust if you can, but it'll work if you have to go somewhere to do it.

    Now everything will be working as it was with the plugged EGR cooler.

    But what if you're making very slow progress with cleaning the cooler and you're getting closer to the expiration date of your permit?

    It occurred to me, that, if you just put back the EGR valve, with the input (cooler) side open, then, depending on how exactly it detects the insufficient flow to throw the P0401, that could make the system think everything is fine, and supress the P0401. As it turns out, there is no sensor before (and after?) the valve (I guess the valve must be "feeling" it somehow), and IT WORKED!

    After I put the valve back in, I cleared the codes. For three days of usual local travelling the CEL did not come back, but the status remained the same: 2 monitors incomplete (EGR and Oxygen Sensor) and P0401 + P0102 pending (which is kinda weird cause i dont remember driving with the MAF unplugged after clearing codes). We had to go on a longer trip for all monitors to complete, and the pending P0401 went away (the other one was still there tho :confused:)

    That was yesterday, and today I put all the wiper stuff back and we PASSED the smog test! Without an EGR cooler!

    NOTE: Having the EGR valve suck in air will maximize the engine rattling (knocking) issue, because the virtual system (computer) thinks there is inert exaust in the combustion, and will time the ignitions in advance, but since there is only air, the combustion occurs too early. So after you pass the smog test, if the EGR cooler still isn't ready, unplug the EGR valve. This will disable the EGR system so the system won't adjust timings for it, and will eliminate the engine knocking, at the expense of the check engine light being on again. But let it remind you to finish cleaning the EGR cooler ;)



    BTW about the coolant hoses. To hook them up I used two 3/4" tees butted together with a close nipple, three 3/4" barb, and one 1/2" thread to 3/8" barb for the small hose, with a 1/2" to 3/4" bushing. I would've used all brass parts but the store was out of stock of the tee and bushing, so I used black pipe instead. Which probably isn't a good idea; black pipe is for gas, and will probably rust, worse than galvanized. But I guess it won't be too bad, since the coolant system is closed, it will only rust until there's no more oxygen. So far I haven't had any issues, and it's only temporary.

    Three of the hoses connected easily, but one of them was too far away! So I had to borrow a piece of coolant tube from an old honda packed in the garage, and I connected it with a 5/8" barb coupling that I just happened to get earlier cause I was thinking of only two coolant hoses...
    And I had to steal some hose clamps from under the kitchen sink :D
    The way I routed the extension hose caused it to crease so later I re-routed it to keep it smooth.


    Pics

    IMG_1195.JPG
    (this was before re-routing extension hose)
    re-routed hose:
    IMG_1210.JPG


    view from below
    IMG_1225.JPG


    blocked exhaust pipe
    IMG_1207.JPG


    the manifold I made
    IMG_1154.JPG


    the dirty little egr cooler
    IMG_1142.JPG


    after everything was put back
    IMG_1235.JPG


    also, ever wondered where the ventilation intake is?
    IMG_1220.JPG
     
    #1 anonymous, Jul 27, 2018
    Last edited: Jul 27, 2018
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  2. tankyuong

    tankyuong Senior Member

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    one way to blow your headgasket
     
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  3. anonymous

    anonymous Member

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    The EGR has been clogged or partially clogged for years, or at least the engine rattling began years ago. A few more days without EGR shouldn't harm anything :)
     
  4. ASRDogman

    ASRDogman Senior Member

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    It would have been a lot easier to just clean it. Or purchase another cooler, clean it and install it.
     
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  5. anonymous

    anonymous Member

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    That's what I did, but I couldn't clean it in time for the smog test. I knew it would probably take days to (discover how to) clean it so I hooked the coolant lines together so we wouldn't be stranded at home. Later I discovered that putting the EGR valve back made the system think everything is fine so we were able to pass the smog test before finishing the cleaning.
     
  6. borgestes

    borgestes Member

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    I like your resourcefulness! One thing I have found, after cleaning a couple is that soaking doesn't work in a timely manner. I found that cutting a metal coat hanger 10 inches long and attaching it to a drill speeds up the process of the oxy clean. clean out the holes and throw it back in the oxy clean and that will speed up the process. Time consuming and dirty but you can use a flash light to see what's clogged and what's open.
     
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  7. ASRDogman

    ASRDogman Senior Member

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    You do what ya gotta do to get by. Then you go back and fix it! :)
    Poking any hard or sharp object in that cooler is risky.
    It would be very easy to puncture the channel then you have a coolant leak.
    For me it would be a very last resort type of thing. If Gunk and Oven Cleaner didn't work, then I figured
    I can't make it any work, it ain't working! So if I did puncture it, so what?
    I'm just very happy I came across Prius Chat and found out about the egr problem and was able to fix it so easily.
    And finding another cooler, and inexpensive.
     
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