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My Mazda is at the dealer for the past 2 days with my list of issues, including (again) the engine temperature.
I don't know details but I've seen on MyMazda that my tire pressures reset and that they put 4 miles on it so hopefully they are doing some testing there.

Btw, not sure how related it is but for me, the issue seems to have happened (or I've started noticing) since I moved and Mazda sits in garage at 55-60F (12-15C) even if outside is 25-40F; I start the car in the garage at 50-60F and seconds later the car is put in a different temperature range; if there's such a thing as ECU adaptation taking place, it could be that this change in temperature that my car gets at start-up might confuse the algorithm (unless was accounted for).
The engine bay is probably even warmer than my garage during daily-drives as this is the garage temperature when I bring the car in (garage heats up from the heat while engine cools down).
View attachment 285217
If the ECU is the one that is commanding these values, it would make sense than why no fault code.
Makeshift experiment: pick 2 days in a row with same morning temperature. Test #1, start car, leave garage as usual. Test #2, park car outside overnight or open garage door maybe an hour before starting the car.

If there's a significant or noticeable difference in reaching OT, your garage theory will be sounding legit.
 

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Now that's a really interesting piece of information! Yes, it's easy to imagine someone making a design mistake by taking the first ambient temp value and not understanding the need to possibly subsequently adjust it. If the stealershp doesn't come up with a resolution for the coolant system issue, you could probably determine if that's the case by leaving your vehicle outside the garage for a day or two. A bit annoying for you, but a big plus if doing so actually confirms what we're speculating here.

Now having said all of that, I seem to recall you posting that your vehicle failed to warm up properly on your way home from Mazda, immediately after they did the last coolant valve swap. If that's correct, it would tend to eliminate the adaptive learning theory being the root cause, at least in that particular instance anyway.
Isn't this assuming that the swap would have necessitated an ECU/PCM reset? I thought I read that for some newer models the dealer sends a specific code to reset the adaptives.
 

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2020 CX-5 GT 2.5L 2011 3i 2.0L
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... I have driven a few separate journeys today and everything seems to be working again, so it must be software related.
If the root cause of your issue is related to adaptive learning by the ECU, then the problem will come back again after some additional drive cycles. Although I suspect the problem will come back, I hope for your sake that it doesn't, because who knows how long it would take Mazda to fix it with a software update.
 
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My dealer is very helpful and there is no problem contacting Mazda Czechia directly. If this ECU "reset" will not help, another step is contacting Mazda directly and wait for an response. I see the problem in the TSB itself. There is no mention about a "reset" of the ECU, so dealer will not do it. I have driven a few separate journeys today and everything seems to be working again, so it must be software related.
Do you use a garage by any chance?
 

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Once I'll get the car from the dealer, I'll put it in my garage and do a measurement next morning and then I'll try to keep my car outside for 2 days and do measurements daily on the same route and see if it changes in any way.
Hopefully the dealer will give me an update today.
 

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Once I'll get the car from the dealer, I'll put it in my garage and do a measurement next morning and then I'll try to keep my car outside for 2 days and do measurements daily on the same route and see if it changes in any way.
Hopefully the dealer will give me an update today.
If this theory turns out right.

🤯

The more I think about it, the more it makes sense; the sudden temperature change is confusing one of the sensors and causing "bad" learning. I wonder if opening the garage door for 5 minutes before starting the car might even be enough to avoid the problem.
 

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Isn't this assuming that the swap would have necessitated an ECU/PCM reset? I thought I read that for some newer models the dealer sends a specific code to reset the adaptives.
I just took another look at the latest P0126 TSB, and didn't see any mention of a PCM reset, however that of course doesn't mean they don't do one. And it's interesting that the FSM procedure for the coolant valve specifies PCM and battery removal. Now it seems to me that there's enough working room to swap the valve without removing that stuff, so I have no idea if they follow those instructions or not. But if they do remove the PCM and battery, that might cause an automatic PCM reset of adaptive values. So I guess we can't know if those values were reset or not, unless it's listed on the paperwork.
 
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I just took another look at the latest P0126 TSB, and didn't see any mention of a PCM reset, however that of course doesn't mean they don't do one. And it's interesting that the FSM procedure for the coolant valve specifies PCM and battery removal. Now it seems to me that there's enough working room to swap the valve without removing that stuff, so I have no idea if they follow those instructions or not. But if they do remove the PCM and battery, that might cause an automatic PCM reset of adaptive values. So I guess we can't know if those values were reset or not, unless it's listed on the paperwork.
I have been told today, that nothing else than ecu "reset" via diag will reset it.
 

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I have been told today, that nothing else than ecu "reset" via diag will reset it.
That's what I meant by "specific" code. They're not only unplugging batteries and draining circuits.

You might be able to do a proper reset with Forscan or other OBD2 tool from home.


Anything better for the gen4 yet?
 

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I have been told today, that nothing else than ecu "reset" via diag will reset it.
One thing that's important to keep in mind is that your vehicle is a hybrid, while (i'm assuming) ours are not. It makes sense to me that the hybrid EV system would keep the PCM active, even if the non-EV battery was removed.

I have not seen anything indicating that, for our current non-EV vehicles, adaptive/learned information is retained, even when the battery is disconnected for an extended period of time. So I would expect that an extended battery disconnect would erase adaptive values for our non-EV vehicles. But perhaps someone knows otherwise and, if so, I'd be the first person in line wanting to hear about it.
 

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One thing that's important to keep in mind is that your vehicle is a hybrid, while (i'm assuming) ours are not. It makes sense to me that the hybrid EV system would keep the PCM active, even if the non-EV battery was removed.

I have not seen anything indicating that, for our current non-EV vehicles, adaptive/learned information is retained, even when the battery is disconnected for an extended period of time. So I would expect that an extended battery disconnect would erase adaptive values for our non-EV vehicles. But perhaps someone knows otherwise and, if so, I'd be the first person in line wanting to hear about it.
We spoke specifically about ecu disconnection. He told me that this does not work on Mazda 6, CX-3/5, etc. You can try and see for yourself ;) There is some kind of small data storage. Not a temp one, but a solid one.
 

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One thing that's important to keep in mind is that your vehicle is a hybrid, while (i'm assuming) ours are not. It makes sense to me that the hybrid EV system would keep the PCM active, even if the non-EV battery was removed.

I have not seen anything indicating that, for our current non-EV vehicles, adaptive/learned information is retained, even when the battery is disconnected for an extended period of time. So I would expect that an extended battery disconnect would erase adaptive values for our non-EV vehicles. But perhaps someone knows otherwise and, if so, I'd be the first person in line wanting to hear about it.
My understanding is that this is no longer correct and that there are both long and short term adaptation values that get stored. The "battery trick" that you're referring to was the dominant method for OBD1, not OBD2.
 

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We spoke specifically about ecu disconnection. He told me that this does not work on Mazda 6, CX-3/5, etc. You can try and see for yourself ;) There is some kind of small data storage. Not a temp one, but a solid one.
Yup. Just like computers. RAM, ROM, etc.

"RAM, which stands for random access memory, and ROM, which stands for read-only memory, are both present in your computer. RAM is volatile memory that temporarily stores the files you are working on. ROM is non-volatile memory that permanently stores instructions for your computer."

Put differently, at best a simple battery disconnect and circuit drain may reset some RAM-like parameters, but only a "reset via diag" will reset the ECU/PCM's semi-permanent ROM memory.
 

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... a simple battery disconnect and circuit drain may reset some RAM-like parameters, ...
And that's exactly where this coolant valve adaptive data MIGHT reside. I say might, because I obviously don't know, and this is all just speculation. And I believe it would be very difficult to find a reliable source which indicates exactly what does, and what does not get erased on a battery disconnect. So I'm not going to spend any more time on the subject of adaptive data. I'll just close by saying that if there is an adaptive data issue with these coolant valves, I hope Mazda can diagnose and correct it ASAP.
 
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And that's exactly where this coolant valve adaptive data MIGHT reside. I say might, because I obviously don't know, and this is all just speculation. And I believe it would be very difficult to find a reliable source which indicates exactly what does, and what does not get erased on a battery disconnect. So I'm not going to spend any more time on the subject of adaptive data. I'll just close by saying that if there is an adaptive data issue with these coolant valves, I hope Mazda can diagnose and correct it ASAP.
Agree with pretty much all of this. I'm more interested finding out if the sudden temperature change of a garage could somehow trigger a coolant malfunction.
 

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I would be able to do some of the tests but when I'll get my car back (probably next week now).
 

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I called today the dealership as my car has been with them for 3 days now but they didn't got to the thermostat yet; I went there with a list of problems and they are replacing my rear differential due to high pitch noise at 60mph.
Next week they will also look at the thermostat but I might not get the car back until end of next week.
 
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