TSB EG-0127T-1014 (SW update to avoid cylinderhead gasket failure)

I guess I don't understand what you're saying here - AFR is much more important to knocking than the presence or absence of a dilution of exhaust gas. However, I'm aware that if the MAF reads higher (because the EGR is clogged for one reason or another) then the ECU will pull timing -- just like any other motor with EGR would. I'm not arguing that point with Toyota engineers or anyone else. And I don't know of any other method of detecting a decrease in EGR flow other than seeing the MAF reading increase for a given throttle percentage.

I'm just making the argument here that local overheating tends to be a cause of blown head gaskets in a variety of motors, and detonation tends not to be a cause of blown head gaskets but rather other kinds of catastrophic failures.

 

Agree to the topic drift. One analogy though:

Say you had purchased a mass-produced boat, and there was a design defect in the hull making it excessive leaky, and the bilge was filling up with water faster than normal. If the boat's designers reprogrammed the bilge pump to run more often and/or faster, would it be short-sighted to say the original bilge pump runtime program was the fault.

 

Look: the engineers specifically programmed the ECM so that if P0401 is present (inability to electrically control the EGR valve), or if P0403 is present (insufficient EGR flow detected), the timing is proactively pulled. It does not wait for the MAF to read higher or lower. It does not wait for the knock sensor. Simple presence of a P0401 or P0403 code pulls the timing to protect the engine.



If you are "not arguing that point with Toyota engineers", then you understand that point. Right?

I see your analogy, but I see no reason to buy the premise. Gen 3 was, I believe, their first use of a variable-speed electric water pump, something they could control in software, to run always at just the needed power level for that moment, and eke out that last bit of efficiency. Some engineer was tasked with writing the control rules to select the pump speed from moment to moment, and the TSB suggests that in that analysis, not enough attention was given to how divergent the temperatures in different places could get, under some of the less-steady-state conditions a Prius engine can find itself in.

The variable-speed, computer controlled water pump and the algorithm for controlling it are among the newest technology in the Gen 3 engine. EGR is not; even though appearing in a Prius for the first time, it had been around for four decades, and even cooled EGR for a decade. It's more like they bought a bog-standard hull, and put their fancy new pump in it.

When they say they got the fancy new pump control wrong, I could conclude one of two things: (1) they got the pump control wrong, or (2) their newly-invented pump control would have been just right on the first try if it weren't for the secretly too-leaky hull.

(1) is believable enough on its own that it doesn't force me to go investing in (2) just because I could.

 

The reason given that I have read for EGR causing HG issues is both because of the clogging of the cooler and valve, but also the clogging of individual passages. That's the whole point I was trying to make. If it clogged cylinder 1's EGR passage but not the other three, then cylinder 1 would get more air, less EGR, and the same amount of fuel, giving it a lean condition.

Losing EGR entirely would be simple for the ECU to deal with - it would detect more air going through the MAF, add the proper amount of fuel, and pull timing back a bit like any car with EGR. It's likely that the ECU would be equipped to deal with this like any other car with EGR.

Losing EGR to one cylinder could cause detonation because it would be running lean. Again, that's what people like Mendel have mentioned as a possible way that EGR clogging could cause HG issues from detonation. But my original point was that I can't see a link between individual cylinder clogging or detonation with HG issues - because of the knock sensor.

 

Again, it's not just Mendel, it has also been me. If you look through the history of who has been posting about it on PriusChat, the emphasis on the individual manifold passages, and also on detonation, has been coming from me.

And I didn't just make it up; in the earlier days of the discussion I was referring directly to engineering literature where the risk of detonation was discussed. However, I did not simply reduce it all to a matter of rich or lean, because the engineering literature doesn't either. The effect of EGR itself—independent of rich or lean mixture—is to vary the speed of combustion, and the number of angular degrees of crank motion during which the whole combustion takes place.

It is weird that you have just written that again, having assumed the same thing in #41. It seems not to be registering with you that the ECM is programmed with specific fail-safe behavior for EGR faults and will pull the timing for that reason. It is not relying on the MAF sensor or the knock sensor to do that. It will, of course, also pull timing as a reaction to the knock sensor, but the EGR fail-safe rules are additional to that.

The relevant lines of the fail-safe chart were attached for you in post #43.

I'm not really sure where your idea of what is "likely" or what is "like any other car with EGR" might be coming from. Are you sure that if you looked in several other cars' fail-safe charts, you would not find that they also have specific fail-safe rules to pull the timing based on EGR function, independent of the MAF or knock sensors? Is there some reason you would assume Toyota would have built those rules into a Prius ECM but not into any other car with EGR?

 

This calibration has been out since August 2014 and we are just now discovering it?!

Also I have a 2015 Gen 3, I assume I already have calibration 34717500?

 

I asked a similar question above. I would assume you have the fix since your car is newer.


iPhone ? Pro

 

The TSB being discussed in this thread was only published in Europe, and yes, last September seems to be around the time PriusChat first heard of it.

And while the European TSB is reasonably forthcoming about what they changed in the firmware, Toyota has not published any US TSBs that are equally candid. My going to the dealer to get the update here is based on speculation that the firmware update they mention—with no explanation—in two different TSBs here from around the same time is the update with the same fix (along with whatever other changes it may contain).

Calibrations IDs are specific to region, sometimes to model year, and sometimes to the original calibration ID that came in the car. So if you look in the European TSB, you see that "34717500" is only the right one if the original was 34717000–34717400, and if the car came with 34730000–34730200 then it should be 34730200, and so on. And all those IDs only apply in Europe. So if you are driving a US Prius in the US, it is pretty much certain that 34717500 is not the calibration that you have or that you should have.

The place I would recommend looking is in the US TSBs T-SB-0103-12. Find the table on page 5 and look up what the recommended new calibration is for your car. (This TSB was later revised, which is why you can look in a -12 TSB and behold, there are 2013s, 2014s, and 2015s mentioned in the table. )

Once again, I'm only guessing that this version in the US contains the same fix they describe in the European version. They haven't said enough publicly for me to be sure (or I haven't found it, anyway). But in any case, it is a later version than the one that fixed another old issue with backfiring and blowing hoses off, so I'm glad I got around to updating it before I ever experienced that.

 

Interesting. In some areas, such as data privacy and product labeling and such, it has long seemed to me that European regulators are less likely to put up with nonsense. Maybe the grass is just always greener....

It didn't seem unlikely to me that the reason the Euro TSB describes what the firmware update changes, and the US TSBs contain not a word of such detail, could perhaps be because the Euro regulators insist on the TSB giving some actual explanation, and the US NHTSA just says "oh, thank you" and files it.

If you insist ... but at the same time, it's perfectly plausible that the revised waterpump algorithm tries to overcome problems caused by many driven miles with a bad waterpump algorithm.

It's as if a vocal corner of PriusChat has long been invested in blaming problems on X, and then a Toyota publication is seen blaming them on Y, and then some from the vocal corner are like, "ok, Y because of X, right?" But Y itself would be adequate on its own to cause the problems, so there's no real need to frame it as because-of-X, except maybe a prior investment in blaming X.

 

My bet would be that the new programming doesn't reduce the pump speed as soon or as abruptly as the old programming did after an abrupt large reduction in engine power output---for example, when we lift off the accelerator to coast down a hill immediately after struggling up it. To avoid hot spots in the engine, increased cooling rate needs to continue for a while to remove and redistribute heat left over from the earlier period of high fuel burn rate. In a non-hybrid, that effect is less likely to be troublesome, because the engine---and coolant pump---doesn't suddenly slow down as much, or even stop, at the crest of the hill.

A physiological analogy: Suppose you're riding a bicycle on a hot day and come to a long hill. You'll feel hotter and perspire more rapidly than you did on level stretches, because you're working harder, or moving through the air more slowly, or more likely both. If at the summit you suddenly stop for a rest break, you'll initially feel even hotter, and sweat even more profusely than on the way up, because you've lost most of the cooling effect of moving through air, yet still need to get rid of leftover metabolic heat from the climb. If you instead don't stop at the top, but continue down the hill before taking the break, you'll get cooling when it's most needed, and be more comfortable during your break.

 

We can speculate, and hope, that the latest update for the USA includes the same (or similar) improvements to pump control algorithm mentioned in the 2014 European TSB, but I gather nobody has confirmed yet that it does. It might not be terribly difficult to see differences by monitoring pump speed before and after updating, under otherwise similar conditions. I worry Toyota might not have updated the US control algorithm IF (which I do not know) US emissions regulations would've required retesting the car to assure compliance.

 

Is it possible for me to confirm that I have the updated calibration on my 2015 Gen3 through TechStream? If so, where would I go to see whatever calibration ID I have?

 

Is there a sticker on the computer to show the calibration ID number? A 2015 may be new enough not to need the update?

 

Calibration IDs for all of the ECUs (that have calibration IDs) show up on the Techstream health check screen.

 

Interesting thought from another angle, sort of like the speculation I had about what they could have changed in the inverter IGBT drive firmware, where the problem was solder joints getting crunchy from cooling too quickly after high power events.

 

Regarding the update version for the engine ECU from T-SB-0103-12 table on page 5.

I've requested a service appointment, but if I reference the TSB and tell them to look up the firmware version on page 5 of the TSB, will they say they won't flash the update because our car isn't throwing any of the referenced MIL codes at the beginning of the TSB bulletin?

Or, should I just request them to flash the engine ECU to 34728500 (2011 Prius) because I want the latest version available?

SM-G781V ?

 

They didn't at my dealership ... I just mentioned there were two different TSBs mentioning the same revision and it was newer than what I had, and they said ok. (I also said I didn't know for sure if that was the latest, and asked them to advise me if they saw any applicable later one, but they just went ahead with the version I asked for.)