EGR circuit... Cleaned it, still CEL. Now what?

You might want call Toyota and check into the warranty enhancement program for assistance. I believe you are within the coverage they have. This is especially true if you live in a CARB state. I might be wrong but the coverage is 150,000 miles/ 10 years

 

I’ve done our egr circuit cleaning twice on our 2010 Prius II now with 184 k miles on it and going strong .

I’ve seen better engine response and improved mpg each time I’ve done this job.

You need to do all components though: egr valve, cooler, pipe and intake manifold. If you miss one, the job is not done.

I have not had misfires or the cold startup knock in a very long time (I also have installed an oil catch can).

Good luck and keep us posted .

 

There are small passages from the egr circuit that go into the bottom side of the intake manifold. These openings get gummy and blocked off.

Since the egr gases take the path of least resistance, if one or more are restricted (or blocked), now there is a temperature imbalance which then can lead to warmer material interacting with metal sealing surfaces while other areas have cooler air interacting with metal sealing surfaces.

Having this thermal imbalance can lead to tee reports you see here of head gasket issues.

I’d get the intake manifold cleaned and go from there.

Good luck and keep us posted .

 

The intake have a small hole for each cylinder that gets clogged. You need to clean them out also.
You beat me to the punch!

 

I had a check engine light one time, and with 5~6 start ups it went away on it's one. That's one possibility. Another: did you make double sure everything's plugged back in: the throttle body connector (likely the car wouldn't run with out), the MAP sensor (just below and to the right of throttle body, as you stand facing the front of engine), the MAF sensor (on the snorkel between air filter and thottle body, one of the last things to reconnect when putting the air box on). I'm guilty of forgetting that one time. The car will run, not bad, on some sort of defaults I guess, but you have constant CEL.

 

This may be a hard code and needs to be cleared with a TecHStream or other similar device. The code data may have been embedded in the source code of the ECM.

 

Various ways to read codes, ScanGuage for example, or some phone apps. Barring that, resign yourself to a dealership visit, get them to read codes, tell you what they are, go from there? Let them know what you've done, don't keep them in the dark.

 

What tool did you use for removing the bottom nut of the cooler? I managed to remove the top and not the bottom. I gave up after an hour of trying. Way too tight in there.

 

Ratcheting wrench.

A great tool for this job.

Harbor freight has them cheap.

 

Are you talking about the blue or red ones? The bottom nut (in blue case) yeah ratcheting wrench helps a lot. The red nut for me at least I found the toughest: really hard to get at. Took just the right ratchet extension length, and really blind. About the time I wrapped up I was watching @NutzAboutBolts video one more time, and see he reached 'round (clockwise around the back of the unit) with his left hand, was actually able to touch the connection that way.

 

Priceless!

 

Just reading now, in the repair manual. Beside the 3 egr components (pipe/valve/cooler), there's mention of the MAP (Manifold Absolute Pressure) sensor being a "trouble area". Did you clean that? It's just below the throttle body, on the right side. In my experience it was completely oil-soaked. If so, what cleaner?

 

Here's the troubleshooting procedure for p0401 (& p0403) . Maybe some can be done without techstream?