Verification of EGR cleaning

Clean it all, at least every 50k miles.

Concur.

 

No, I was talking about the routine self-test done by the car, whose result you can look at by retrieving the mode-6 monitor result.

 

That’s a non-continuous monitor and not an active test. Those are different. Both have a value for EGR verification.

The test result is a pressure delta between when the EGR valve isn't open and when it is.

That is not my interpretation of this monitor value. It does not include/know the position of the valve, it’s just a straight up monitor average of MAP flow compensated for potential open/close abnormalities. As you will likely disagree, please supply information how this event is included.

I would recommend to test/use the active test if they have TS - and want to test the valve open/close effects on flow kPa prior to pipe and manifold.

This data can indicate issues with the valve being clogged/obstructed.

 

Sure, but that’s not preventive in my book, it’s active remediation.

It’s indeed a DIY and should be done, but it seems impossible to prevent due to the engineering design flaws,

 

Semantics?

 

Not really. But; Let’s leave that focus alone (I could go on and on..).

It’s very relevant to clean the EGR.

There is no way to prevent it. There are some ways to verify it.

Merry Christmas to y’all.

 

Post #15 upthread explained how and when the ECM's self-test is performed.

If enough time has elapsed to repeat the test, or if a code clear has been done and the monitor status is incomplete, the ECM will wait for the next opportunity when:

• the engine is warm (70 ℃ or more)
• RPM is 950 to 1600
• operation is fuel-cut coast or decel (fuel has been cut for at least 2 seconds)
• the engine load has been stable for more than 1.2 seconds
• RPM is holding constant within ±20 RPM

Under those conditions, the fuel-cut, spinning engine is pumping a stable vacuum (down around single-digits kPa absolute pressure) against the closed throttle plate. The ECM recognizes that opportunity and conducts a three-second test in which it notes the MAP reading with the EGR valve closed, notes the new reading with the valve opened a certain amount, and subtracts the first from the second. The result is recorded as the monitor value.

If the stable test conditions don't continue long enough to complete the test, the result is discarded and the ECM continues to wait for the next suitable opportunity.

If you live in a jurisdiction with inspections, and an inspection is coming up and the status of this monitor is incomplete, you can hurry completion along by following the "confirmation driving pattern" given for P0401 in the repair manual, which is nothing more than driving so as to create a suitable opportunity for the test on purpose. Or, if there is no hurry, you can just keep driving the car normally and the test will be conducted as soon as the right conditions arise in your normal driving.

 

@ChapmanF I know how monitors work. It’s not the same as the active test - that is only available with TS as I understand it.

Can you please, with so much knowledge, ever mention some other knowledge or input as also relevant or ballpark correct?

As many likes as you have received, you could also deliver some, at least for that holiday spirit. Not to me, but anyone. It would be refreshing.

Merry Holidays!

 

I'm in no position to judge how much you do or don't understand about noncontinuous monitor tests in general. All I could do was notice you had written this, about the particular (module $31 test $bd) NCM for EGR flow:

which was not even close to correct as a description of how that particular NCM works. During the three second interval while the ECM is conducting the test, it drives the valve to the closed and a somewhat open position, notes the MAP readings both ways, and subtracts.

We agree that scan-tool "active tests" are different from noncontinuous monitors. With a scan tool, you can override the EGR valve position to any step value, and make your own notes about the response of the engine. You're doing it all manually when you do that. It can be handy sometimes as a troubleshooting technique.

But agreeing that manual active tests can have their own useful place in the troubleshooting toolbox does not have to go hand-in-hand with misstating how the automated test works.

It's also worth noticing that it would be really hard (and definitely need a second person in the car while you drive) to try to use the active test feature of a scan tool to duplicate what the ECM itself does within three seconds every time it repeats the EGR flow NCM test.

I wonder a little, from the way you described your idea of how the EGR flow monitor works, whether you might be mixing up continuous and noncontinuous monitors a little. As a noncontinuous monitor, this is not something that just hoovers up data all the time and computes some kind of average. At the specific, noncontinuous, times that it runs, it takes specific actions and records the results of doing so.

The active tests are available in a variety of scan tools / apps. You generally have to look at the more-commercial ones (like the Autel) that have a revenue stream and can afford to license the details from Toyota. The purely open-source efforts have done a remarkable job reverse-engineering read-only details like PIDs, but it may be harder to crowdsource reverse engineering of active test commands on things people paid $40,000 for.

Filtering the snide out, what's left of that seems to be a request for my source for how the EGR flow noncontinuous monitor works. You also requested that in #16 upthread, and I gave the source as promptly as I could in #18 (the only reason it wasn't in #17 is #17 was another post from you). You obtained that and attached it yourself in #19.

So I'm not sure what to say at this point. If we're reading the same description of a noncontinuous monitor and you think it's talking about some kind of continuous averaging, it might take more specific questions about the text to iron that out.

 

…which was not even close to correct as a description of how that particularNCM works. During the three second interval while the ECM is conducting the test, it drives the valve to the closed and a somewhat open position, notes the MAP readings both ways, and subtracts.

Well, it’s still not even close to an active test of the valve function. It’s a very good indicator of throughput and is valid analysis data. But you misintrepet the main data question.

It’s a monitor value based on repeated cycles with a temporal preprogrammed sequence.

The active test is different. Do you disagree?!

Or can you not just accept the active test mentioned might also be of relevance?

 

It is beyond me at this point how you can quote what you just quoted ("it drives the valve to the closed and a somewhat open position, notes the MAP readings both ways, and subtracts") and also say that doesn't test the valve function and flow. Could you explain your thinking on that more clearly?

When I said this:

was that me in some way not accepting that the active tests might also be useful for something?

If so, can you try to more clearly explain what it is I haven't accepted?

 

We seem to have a case of unstoppable force meets an immovable object, which in reality is impossible.

However the heart of the issue may be the Toyota/TCCN position on egr cleanings as a hg preventative measure vs the Mendel/Priuschat frequent maintenance view.

Personally, as a vested interest with two previous gen2s and a current gen3v (v with 345k miles/555,000 km) I believe there is no silver bullet. Toyota revised many hardware and software components of gen3s by 2016 and kept selling them overseas through 2021 with little issues in those last years.

More revealing from a forensic viewpoint are engine changes for gen4 which resulted in a solution with an excellent track record. Egr intake rerouting, cylinder cooling redesign, head gasket geometry, cylinder head redesign and more.

My take for the used car buyer: Don't buy a gen3. If you have one and it burns oil, change the piston and rings just as Toyota did for many thousands when the gen3 issues first surfaced in the early years.

PS Egr flow sticking open shakes are far different than the severe head gasket metal to metal death rattle which sounds like a broken connecting rod.

 

What was the miles cutoff for eligibility for piston/ring replacement, 60k? And when does the oil consumption usually take off, about 150K?

I doubt Toyota will ever say a word on the subject of EGR cleaning, basically "taking the fifth".

 

In that same spirit, Toyota refuses to clarify the difference between 17120-37054 and 17120-37091.