Can P0401 be related to MAF sensor?

Hi all! Sorry for creating a new thread on P0401, but digging through the existing ones did not help me.
I need your advice on the following problem as I am quite desperate now:
- Prius 30 from 2011 (125k miles).
- In the summer (~5 kmiles ago) I cleaned EGR, cooler, intake manifold - basically everything related to the EGR preventively. Actually, it did not look as bad as on some of youtube videos, but I still thoroughly cleaned it all. The car was driving fine before and after.
- A few weeks ago I decided to clean the MAF sensor (the one that is sitting at the intake pipe close to the air filter). Used a special MAF sensor cleaner like shown in youtube videos.
- A couple of days after that I started getting P0401 (Exhaust gas recirculation flow insufficient detected). I can clear the error but after a day or so it comes back. It comes back always when the engine is more or less warm (never at the start or in the first 10 min). It seems that it goes ON when the engine shuts off while driving (e.g. when driving downhill) and then starts again.
- Further I feel no change in the way the car drives.
- Decided that my EGR went bad and replaced it. Unfortunately I could not get a new EGR and used a refurbished one (they are selling such in Europe). When replacing EGR checked the cooler and the pipe towards the intake and cleaned them again. They looked good and clean but I still cleaned ones more.
- The error came back in the same way as before.
- Replaced the MAP sensor (the old one was a bit oily). It did not help at all.
- Removed and cleaned the intake manifold again and replaced all the seals on it (except of the one for the throttle body (I did not have a new one, and it did not look bad). The passages for EGR were not blocked but I cleaned them again. The problem (P0401) returned next day as usually.

Now I am out of ideas. Can this be related to the fact that I cleaned the MAF sensor and could damage it while doing that? Or is this completely a coincidence and I should blame the refurbished EGR and go get a new original one (quite expensive!)?

 

Thanks for the quick reply! I did clean the entire thing: the cooler, the intake manifold, the pipe (which is between the valve and the intake manifold) and replaced the EGR valve with a refurbished one. I did not notice any blockage anywhere. The cooler is perfectly clean. I tested it with a hairdryer blowing air through. Same test I have done with the intake and all EGR channels were letting the air through. I did not notice any blockage on the pipe that is connected right on the exhaust. In fact, when I removed the EGR and the pipe I noticed quite a bit of moisture inside of them. That can only be the water condensation from the exhaust, which means that the gas does come to the pipe and to the intake manifold.

 

The wiring looks Ok, but this sounds like a good idea to check it ones more.

I have not yet done this test. Will run it tonight. Thanks!

 

Well, I have understood that I need a Techstream scanner and SW to run the test as suggested, which, unfortunately, I don't have. I have only a simple wired OBD2 scanner, but it allows reading the data live. I went for a drive while recording (on my phone filming the scanner screen) the MAF, MAP sensors, RPM and EGR PTC. It looks all Ok to me: EGR gets open, when it gets open the pressure in the intake goes up. MAP sensor readings were in between 102 kPa (engine off - atm pressure) and about 25-35 kPa when the EGR closes and the throttle is also closed (at that moment MAF also shows low value, like 1-2 g/s).
Unfortunately, while driving I could not reproduce the error: the code did not pop up in about 15 min drive I had. I guess I need to run longer while recording the data and catch the moment when the code pops up.
I feel like the EGR itself is faulty. It might hang at a certain position once in a while or something like that.

 

Hi all. I decided I should give an update. I have bought a new, genuine Toyota EGR (530 EUR) and installed it. I am driving now for the third day and no error popped up yet.
Actually, I think the problem might have been not in the EGR itself but in the gasket and my stupidity and lack of experience. When I cleaned the EGR in the summer, I did not have new gaskets for it. The old one looked a bit damaged and what I did - I have put a bit of loctite on the surface of the gasket and tightened it assuming that it will work as a kind of a sealant. When I have installed the remanufactured valve I have put new gaskets, but did not clean the surface of the heat exchanger from the remains of the loctite. Most probably, because of the loctite, the gasket did not seal well and it was leaking gas a bit, especially when warm (expanded). Now I cleaned the surface well and installed a new gasket again, but, since I have a new valve as well, it is hard to say what actually has fixed the problem.