Advice Needed! P0401, P0300, P0301, P0303 Head Gasket and/or EGR?

Thank you @rjparker! The noises I'm hearing now are not the normal initializing noises (whish I could post a video). Do you think doing a break bleed would help? (still need to find the right OBD2 tool for it :s ). Do I have to replace the ABS module if I replace the break booster/master cylinder?

No HV battery codes yet, no other issues other than decreased mpg. What would be the best place to get a good deal on a new OEM battery?

I think it's been 3 weeks since the initial "incident" that started this post. So far the car has been running fine, oil and coolant levels stable (no loss), no overheating whatsoever, haven't done the exhaust test yet. Any other symptoms that I can monitor for a bad head gasket?

Thanks again for the help!

 

Thanks @Mendel Leisk!

 

It’s been almost two months since the incident and the car seems to be running “fine”. No overheating whatsoever, oil and coolant levels stable, it has never had the morning rattle/shaking, not other sure what other head gasket issues signs to look for, is it too early still to discard the possibility of a bad head gasket? It looks to me that the most likely culprit was an improperly gapped or defective spark plug but I know that would be the best case scenario and don’t want to make a bad decision based on feelings.

Yesterday my wife told me that the check engine light had just turned on, surprise surprise, is code P0401! I just purchased the Autel Maxi AP200 scanner, are there any tests I can run with it or any data I can read with the scanner that would help me identify wether there is too much or too little flow?
From what I’ve learned, the code is not always triggered by a clogged EGR system. I just want to discard a bad ECM before I tear into it again.

What would you guys do? Thanks again for the help!

 

Awesome! @rjparker , do you know if such test can performed with the Autel AP2000?

 

Hello @Mendel Leisk, it was a typo, I think back then it had 180k (now has over 181k I believe). I went ahead and took advantage of a "cooler" weekend (under 110 degrees) and with the help of a friend took the EGR system apart and cleaned it really good (see post #44, third page I believe). I wonder what can be triggering the P0401, I did not have the P0401 (or any other codes whatsoever) before the incident. After I replaced the spark plugs, all codes went away, no driving issues. I learned about the Prius clogged EGR problems while researching probable causes for the "incident", that is the only reason I decided to clean my car's EGR system. I mentioned before that the intake manifold passages were relatively clean and not obstructed at all. The cooler was dirty but I could still see light through it, it was not completely clogged. The car has been driven for almost two months after the incident, around 1k miles and no signs of coolant leaks, no overheating which gives me hope the head gasket might be ok.

Do you still think it could have a faulty head gasket? Like I mentioned, I don't want to convivence myself the car doesn't have a head gasket issue just because I would really like it not to have it. If the head gasket is still good I'm planning on replacing the break master cylinder once I find a scanner that can handle ABS system bleeding. I'm also looking for new OEM traction batteries (if anyone has a source they recommend for a good deal please let me know).

From what I have read, some people have experienced the P0401 code after cleaning the EGR system due to - Stuck EGR Valve - Bad ECU -Bad MAP sensor. Are there any other common causes for the P0401 code after cleaning the system? Not sure if a loose connection might cause something like this but I will check all the connections again this weekend as long as the test RJParker suggested.

As always, I immensely appreciate your thoughts and feedback, please let me know

 

I guess I will find out this weekend when I get my scanner, thank you RJParker!

 

1.- Yes, sorry I was not more specific. The small EGR passages where not obstructed at all, just a thin layer of build up. I cleaned them anyways

2.- Gotcha. Any conclusive test that I can do to make sure? Like I mentioned, I don't want to invest more time and resources in the old car if the head gasket is bad.

3.- Yep, good thing I found out before it got worst and was able to clean it really good. Now I have to figure out why it is giving me the P0401 error after getting it squeaky clean. Any pointers?

 

I was reading another thread where @ChapmanF helped another forum member research and I believe fix his car’s issue. Could it be something as simple as this?

 

Hello @Mendel Leisk, how did I miss that! Thank you and sorry! (Edit: I just realized you just posted that response to a comment on mine a just made a few minutes ago on a different thread, not this one. Makes me feel a little better!)

Yes, that is the cap that I just took off yesterday, I’m not 100% sure I actually switched to the one I had not previously installed so I’m going to compare the two and install the better one. The one in the pictures seems to be good enough to stop the spring.

Will JB weld or a similar high heat tolerant epoxy be good enough to repair the ramp if needed? Has anyone that has repair it successfully can share how they did it and what they used?

I’ll take pictures of both and report back.
Thank you!

 

Thank you @ChapmanF, I'm not so sure about the hot knife (never tried doing something similar to that). I have a "plastic welding gun" that I have not used, not sure if it is small enough to fit there and also not sure what material to use (I don't think I have "extra" to scoop back on top like @ozmatt did).
The screw fix seems too risky. I was hoping for something a little simpler like epoxy.

Also, I'm not sure I understand the ramp's purpose. It looks to me like that it serves as a stop point when the magnet is fully treaded and the flat/taller side of the ramp comes in contact with the little metal stop on the little washer-looking round metal at the end/beginning of the threaded rod on the valve. Does that sound about right?

 

@ChapmanF thank you so much for taking the time to explain it to me. What would be your theory as to why does the ski jump (ramp) deteriorates? The ECM sending 111 (or so) pulses when the valve is not fully open causing wear over a long period of time (14 years, 181k miles in my case) and when the plastic is also very hot?

I've been playing with the replacement valve that I have outside the car right now (don't recall if it is the original that my car had or the replacement that I bought to clean before hand so I could save some time) and I can "feel" how if the magnet is threaded ever so slightly after it reaches the valve stop point, it will get stuck and will not allow the spring to push the magnet out and unthread by itself.
When I take the inner spring out, the ski ramp makes better/lower contact with the little metal valve stop point and it does not get stuck. If I keep the magnet slightly up (kind of simulating the force of the inner spring) I can feel where it gets stuck.

So interesting that such a small and simple thing can cause so many issues...

Will report back with my findings in case it is useful to anyone.

Thanks again for all your help @ChapmanF, @Mendel Leisk, and all others!