Cataclean and EGR Clog Codes

Discussion in 'Gen 3 Prius Technical Discussion' started by C-in-DC, Feb 21, 2023.

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  1. ChapmanF

    ChapmanF Senior Member

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    Is P0401 the only code you're chasing now, or are there still other things going on?

    Does your MAP reading seem reasonable? How does it compare to the weather service barometer when the engine is off? What does it say when the engine is idling and there's no EGR?

    What does it do when you try commanding the EGR open a dozen and a half steps or so?
     
    #201 ChapmanF, Apr 11, 2023
  2. C-in-DC

    C-in-DC Member

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    I have two codes b1423 (ac leaked out, different thread) and p0401.

    Map sensor seems to be reading consistently. It's at 15.15 psi with the engine off. Barometer is at 30.29 inHG(14.877 psi) here. Map sensor reads 4.35 to 4.5psi when the engine is idling.

    Egr step position test parked after driving 40 mph for 15 minutes. Car's in maintenance mode.



    I gotta long drive tomorrow up to western MD so I can record egr conditions at highway speed if that's useful. It's a new map sensor from the dealer and it's basically reading the same range as the old one. I think I'll swap out the maf sensor for aftermarket soon. I can get a used air intake manifold for 125. New ones out of my price range.

    The air cleaner box has a Crack in it that I sealed with duct tape. I don't think that's the cause of a leak but what do I know...
     
    #202 C-in-DC, Apr 11, 2023
    Last edited: Apr 11, 2023
  3. ChapmanF

    ChapmanF Senior Member

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    I'm not convinced your EGR valve works. Or the flow is seriously blocked somewhere. It seems to raise the MAP reading a bit at 1 step, but not appreciably more at 20 or 30. I would expect the engine to sound awful or stall outright at 20 steps, let alone 30.

    What's the EGR monitor test result?
     
    #203 ChapmanF, Apr 12, 2023
  4. C-in-DC

    C-in-DC Member

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    What
    I can do a EGR step position test and see if the egr vvt monitor is complete or incomplete. Can't get more info. Perhaps one of the other tests equal thr monitor test?
     

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    #204 C-in-DC, Apr 12, 2023
  5. C-in-DC

    C-in-DC Member

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    I have not checked the exhaust manifold for blockage. Will be doing that soon when I change the gasket.
     
    #205 C-in-DC, Apr 12, 2023
  6. C-in-DC

    C-in-DC Member

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    Live data stream
     
    #206 C-in-DC, Apr 12, 2023
  7. ChapmanF

    ChapmanF Senior Member

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    Mode 6 monitor result retrieval should be someplace else, separate from active tests.

    For EGR it is a pressure reading (usually in kPa but sometimes a scan tool will convert to psi etc.). It represents how much the MAP changed when the car did its own most recent EGR self test.
     
    #207 ChapmanF, Apr 12, 2023
  8. C-in-DC

    C-in-DC Member

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    I could download egr function for $50 bucks but I don't think it'll show anything different than what I have
     

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    #208 C-in-DC, Apr 12, 2023
  9. C-in-DC

    C-in-DC Member

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    Confirmed it's for other makes not Toyota and now I'm out 20.

    Figured I could change the exhaust manifold gasket without draining down the coolant. I guess the coolant will leak out the egr?
     
    #209 C-in-DC, Apr 12, 2023
  10. ChapmanF

    ChapmanF Senior Member

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    If the EGR cooler doesn't have a leak between the exhaust side and the coolant side, and you manage to just move it out of the way with the hoses attached, I don't see why any would leak.

    What kind of nickel-and-dimey scan tool are you using that won't just do a mode 6 query without an in-app purchase?
     
    #210 ChapmanF, Apr 12, 2023
  11. C-in-DC

    C-in-DC Member

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    Thinkcar ThinkDiag
     
    #211 C-in-DC, Apr 12, 2023
  12. C-in-DC

    C-in-DC Member

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    I opened the 2016 EGR to see if I could use the sky jump only. Unfortunately they’re different sizes but both are step motors. I’m hesitant to buy a new EGR valve but it’s looking like that’s the only fix other than changing the intake manifold. Maybe something will be found in the exhaust manifold
     
    #212 C-in-DC, Apr 12, 2023
  13. Mendel Leisk

    Mendel Leisk MMX GEN III

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    If you need to disconnect any coolant hoses at EGR:

    Take a look at second link in my signature: you can preemptively drain a couple of quarts/liters into a clean container, which is enough to leave the EGR components virtually dry (apart from a few tablespoons at lower back corner of EGR cooler).

    When everything is back together pour those 2 qts back into reservoir.
     
    #213 Mendel Leisk, Apr 13, 2023
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  14. C-in-DC

    C-in-DC Member

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    The EGR valve is an aftermarket manufactured either in Malaysia or China. It’s long past the return period. I could purchase a Toyota EGR valve and take the $100 loss on the aftermarket. Toyota with a discount is around $270.

    has anyone ever confirmed a brand for an aftermarket egr valve?
     
    #214 C-in-DC, Apr 13, 2023
  15. C-in-DC

    C-in-DC Member

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    So I changed the exhaust manifold gasket. immediately got smoke when the car started up. There was no blockage in the exhaust pipe that goes to the egr. I couldn’t put the lower gasket in because the OEM spring bolts are too short. the bolts that came with the magna flow cat are longer but I wasn’t able to put them on because I ran out of time. Thinking the cat to the exhaust manifold gasket or lack thereof could be allowing exhaust to escape at the connection and providing lower exhaust fumes that could cause p0401. Also might be overheating in the engine bay which is not good. But I don’t know how the egr monitor measures the low flow insufficiency.
     
    #215 C-in-DC, Apr 16, 2023
    Last edited: Apr 17, 2023
  16. C-in-DC

    C-in-DC Member

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    Couldn’t find the magnaflow hardware. I guess the mechanic who welded the cat or I threw it away. For some odd reason engine mounting bracket bolts are the same size threads as the exhaust manifold bolts, 14mm head, and more than adequate length. The felpro lower exhaust manifold gasket is in. Car sounds different while accelerating. Sounded like the exhaust had a hole in it before.

    So all gaskets have been replaced from exhaust to egr to intake to throttle body.

    Checked the exhaust manifold for leaks. None found. It’s down to the intake manifold or the egr valve or an outside the loop problem. If the code comes back next move is changing the intake manifold.
     
    #216 C-in-DC, Apr 17, 2023
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  17. ChapmanF

    ChapmanF Senior Member

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    You could read about it. It's covered in the description of the P0401 code in the repair manual.

    Toyota Service Information and Where To Find It | PriusChat

    The test is run during normal driving when certain conditions are met (they are all listed in that troubleshooting section). The ECM will then pick a moment when you are decelerating with the engine spinning and the fuel injection cut off, and it temporarily opens the EGR valve by some amount and watches the MAP reading to see how much it goes up. The reading should go up, because the open EGR valve should allow more gases to enter the manifold.

    So if the MAP reading was n kPa before opening the valve, and it goes up to m kPa with the valve open, then the difference, m − n kPa, is saved as the result of the test, and you can use a Mode 6 monitor results query to look at what that result was from the most recent test the car did.
     
    #217 ChapmanF, Apr 17, 2023
  18. C-in-DC

    C-in-DC Member

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    This could be the fuel injection cut test with a data stream monitor. My scan tool is very limited compared to techstream.
     
    #218 C-in-DC, Apr 17, 2023
  19. ChapmanF

    ChapmanF Senior Member

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    No—like most of the car's emission monitors, it is a self-test that the ECM automatically runs when it chooses, based on certain driving conditions being satisfied. You're not going to find it looking among the active tests you can perform from a scan tool.

    You can, however, use a scan tool's Mode 6 monitor result inquiry feature (look for a separate menu or whatever for those) to find out what the result was, from the most recent time the car ran the self-test.

    Mode 6 inquiries are a standard OBD-II thing, and a lot of scan tools can do them, though maybe not all, and would have to be found in the instructions for whatever scan tool.

    We have a thread where people have been posting their EGR monitor results and using a variety of different scan tools to do it.
     
    #219 ChapmanF, Apr 17, 2023
  20. C-in-DC

    C-in-DC Member

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    #220 C-in-DC, Apr 17, 2023
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