Still P0401 after cleaning egr !! should we drive it?

EDIT-. Not sure this is correct my T-SB says USA market and you're in Australia. Best check with a local dealer for revised part #...

Try the revised EGR part number 04004-58137, 25685-37010 (gasket). I'm afraid it may need a ECU reflash.

moto g(7) power ?

 

We have this here but if you see it says "Market USA"


I actually flashed it myself at home even though it is still warrantable because of the T-SB. But this for LHD. Don't know if it's the same part # for you. So I have the old EGR valve but new programming. Probably need the dealer unless you have a compatible VIM and subscribe to Toyota TIS...

moto g(7) power ?

 

Mine started making a ticking type noise one very cold morning. (Only that cold morning). It was so prominent I thought there was an animal under the hood. (Back then I didn't know about this T-SB). I opened the hood but no animal was there. We use high grade fuel in ours 91 AKI when the manual asks for 87 AKI, so the anti-knock properties of the fuel should have helped.

Beyond that I don't know much. Maybe you can call a dealer with your VIN and see if yours is an affected vehicle?

moto g(7) power ?

 

P0401 is set when the ECM tests out the EGR valve during deceleration driving, opens the valve, expecting that to change the manifold absolute pressure reading by more than 1 kPa, and it doesn't.

Have you done any of the testing shown in the manual or in the valve blockage data thread?

What are the MAP readings with the EGR open and not open? What's the MAP reading with the engine stopped? Is it plausible?

 

I think it's kind of normal to end up with the pintle slightly open after you have reassembled the valve. That gives you a nice opportunity to shove it closed with your thumb, which should feel and sound as if you are pushing a smooth nicely-lubricated spinny thing. It's kind of nice that you get that natural chance to confirm things went right.

If it isn't quite closed when you start the engine, I think it should be closed very quickly after that. If the waveform info given in the manual is to be believed, the ECM uses about the simplest possible strategy for figuring out where "closed" is: it just keeps trying to step the motor in the closing direction at all times when the engine is idling. That should pretty much end up getting to closed no matter where it started.



The total travel between fully closed and fully open is said to be 110 steps (111? not remembering exactly). How fast it covers that distance depends on just what they're calling a 'step'. The wiring diagram and waveform show that they're using the "two phase on" strategy described here, and if they're using the terminology the same way, one 'step' would be what happens each time one phase is switched. The waveform shows that happens every 50 ms, which would mean a stepping rate of 20 steps a second, meaning it could get from full open to full closed in 5½ seconds (if nothing is stuck). Surely yours was nowhere near fully open no matter how hastily you put it together.



That manual excerpt says you should see the waveform when "idling with warm engine". Does that mean they aren't sending "close" steps right away from engine start? That seems like a weird choice to me, but maybe that could explain your minute of weirdness. Or the weirdness could have been something else and the "with warm engine" could be a goof in the manual.

Sounds like another question for a sunny day and an oscilloscope.

It is easy to mix up MAF and MAP. The sensor that matters for EGR flow checking is the MAP.

I don't remember whether I was using inspection mode when I played with that last. If you don't, and the engine shuts off while you're playing, then sure, inspection mode will prevent that. I don't think the ECM usually changes behavior much just because you have an active test window open in Techstream. The only behaviors result from the active test commands you actually send.

 

Almost makes me think the valve is opening/closing as commanded, but somewhere in the EGR flow path there is still an undiscovered severe restriction....

 

You know I wondered the same thing. If people are cleaning the EGR system what about the exaust pipe beyond it? Looking at it with a flashlight there was some build up in there, but it didnt look major.

It would be a pain (and maybe not fix your problem), but I guess you could take off the cooler and put a borescope down the exhaust? Perhaps the clog actually would be quite close and visible via flashlight?

And after putting that gasget on myself I can see how someone in a rush could make that mistake. Was having a lot of time getting both the bolts to thread through the hole in the gasget and into the cooler. I worked for about 30 minutes in a very awkward position before I got it correct.

 

Not everyone knows the answer, like me. Glad you're in good hands...


moto g(7) power ?

 

The test value is the amount the manifold absolute pressure changes when the ECM opens the EGR valve by a certain amount to let gas flow in. It's essentially the same test you were using Active Test to do, only done from time to time behind your back automatically by the ECM during driving while you are decelerating.

 

If the "minute of roughness' only happened the one time, it's a commonly reported thing for the first run after an EGR cleanout. It happened to me on our 2010, which ran scary rough for what felt like a lifetime on the first start and threw a code. That went away and didn't come back. On our 2012 I made extra sure to air out the carb cleaner, and it started up without a fuss. So no worries there unless it keeps happening.

Given the symptoms of an apparently operational EGR valve (demonstrated by Techstream-commanded steps) and the P0401 by the fuel-cut operation trigger, I'm wondering if you have an EGR leak due to a missing gasket. That would explain those symptoms IMHO. The valve could be working fine, there could be no restriction, but the expected EGR is blowing out the leaking gasket. The computer says "hey where's my pressure?" P0401.

 

Well, keep in mind that the "A" in "MAP sensor" stands for "absolute".

When you see those MAP values of "4 psi" during testing when the EGR is closed, that's 10 or 11 psi below atmospheric—a decent vacuum.

If there's a leak, when you open that valve, you'd probably still see that MAP reading go up, whether it's the exhaust gas you were expecting or just the surrounding atmosphere rushing in through your leak.