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Sure sound like a thermostat issue....Find the specs for your thermostat and test it. Up until recently the specs are such that the thermostat should be at least partially open starting at 177°F and fully open by 203°F. Operating temperature should be consistent at about 185°F driving normally, up to about 205°F give or take a few depending on driving conditions, ie driving up long grades, ambient temps etc.
Test the coolant with a thermometer if you can and compare it with the gauge, see if its close.
Is your OBD scanner capable of logging cooling fan on/off cycles?
Thermostat was replaced under warranty on Monday and it’s an electronic one (see my previous post).
My scanner doesn't seem to have the option to log the cooling fan.

Did you have the interior heating on during this test, or was the climate control entirely shut off?
I've done multiple tests with and without climate control and it didn't made any difference.
 

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Thermostat was replaced under warranty on Monday and it’s an electronic one (see my previous post).
My scanner doesn't seem to have the option to log the cooling fan.
Electric or not, there should be operating specs (voltage, open/closed signal, temperature readings etc) that can be used for diagnostic purposes. If its electronically operated, its function is monitored by the PCM and / or the ECU. There should be a way to monitor what its doing if its controlled by either of those.
 

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Thermostat was replaced under warranty on Monday and it’s an electronic one (see my previous post).
My scanner doesn't seem to have the option to log the cooling fan.


I've done multiple tests with and without climate control and it didn't made any difference.

Thanks, then two more stupid questions from my side:

- Have you had the opportunity to check both the engine oil temp as well as the transmission oil (ATF) temp to see how they have behaved? --> In case they have not been fully warmed up, they will act as an additional thermal sink during downhill driving

- Do you have access to the throttle position signal (not the accelerator pedal but the actual throttle position) during the same driving conditions? Is the throttle fully closed or somewhat open during downhill driving when the accelerator pedal is completely released?
 

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Engine oil temp doesn't show up on my interface (it is in the menu but it doesn't show it).
My interface is pretty basic and doesn't have a lot of features.
I've mostly done all these measurements out of curiosity as the car is under warranty and I don't wanna fiddle with anything that they could blame me; reading OBD2 I think is pretty harmless. Dealer said they will contact Mazda and come with a response. I have 1 more year of warranty and I will trade it for some other (non-Mazda) car before it expires.
 

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Electric or not, there should be operating specs (voltage, open/closed signal, temperature readings etc) that can be used for diagnostic purposes. If its electronically operated, its function is monitored by the PCM and / or the ECU. There should be a way to monitor what its doing if its controlled by either of those.
I couldn't find much by looking at the service manual apart from the one page bellow which I want to add it here to have it handy for others.

Font Parallel Screenshot Circle Number Font Slope Parallel Electric blue Diagram Product Font Parallel Screenshot Electric blue
 

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This BMW thing is normal for BMW. When driving in "ECO style", the Temp rises and when driving hard, it drops. You can find about this on many websites.
 

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2020 CX-5 GT 2.5L 2011 3i 2.0L
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I've picked up my car and the problem is still there. Dealership doesn't know what next and they are going to call Mazda tech for support.
They gave me a CX-5 as a loaner yesterday and on that exact route on the motorway, after 3 miles it got to operating temperature and stayed there; I drove my car 14 miles today and it never got to operating temperature; the most it got was halfway and then started dropping (seemed even worse than before).

Looking at the details the part number they put is PYFD-15-16Z and they followed SA-035/20.
It could be simply that the replacement control valve was bad right out of the box. It's unfortunate that this part is currently so scarce that they probably don't have another one in stock to try.

And there also seems to be some confusion on the part number as well. The most recent TSB that you posted gives the replacement part number as PYFB1516ZA, however the online parts sites show that was superceded by PYFB1516Z, which is the one on your paperwork. That seems odd, because they usually add letters to the newer part number, not the other way around. So something is not right with all of that.

I'm very familiar with this whole thing, as a result of CX-5 owners posting the same issue on those forums, and both the CX-5 and the 3 have the identical control valve installed. And there are a couple of particularly troublesome aspects about this coolant valve problem. The first big problem is that there are no testing specs currently provided for the coolant valve in the FSM, which means that the ECT temp, or an OBD code is the only way to know that something might be wrong with the valve. However, there's currently no way to do any testing to confirm the valve is malfunctioning. Mazda is telling the stealerships to just hang on a new part, which IMO is a really weak effort on their part.

And, dovetailing with the first concern, is the fact that Mazda has provided no indication of what the problem with the valve is. There are three main components (actuator, sensor, and thermostat), and it's anyone's guess as to which one of them is causing the low coolant temps, or high temps for that matter as well.

And just as an FYI, the normal operating temp of the CX-5 equipped with this coolant valve is typically around 195F, And if idling when fully warmed up, the fan will come on at 212, and shut off at 195. IDK if your 3 has those exact temp specs, but it should at least be very close.

I'll be interested to see what Mazda comes up with for a resolution for your vehicle's problem (and hopefully it won't take them a long time either).
 

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PYFB1516Z, which is the one on your paperwork. That seems odd, because they usually add letters to the newer part number, not the other way around. So something is not right with all of that.
The part I have seems newer as it starts with PYFD-*.

Thanks for the insight. I went to the car and I can confirm that the part code is PYFD-15-16Z (matching what they put on the file) as you can easily see the part number however I haven't check what was the old part number.
The dealership doesn't seem to have tested the car after they replaced the part and I'm waiting for their phone call.

Just by looking at the graph I posted here here, it seems that the temperature is climbing pretty constantly until ~130F and from that moment it kinda goes flat; I wonder if it's a bad ECT sensor and maybe the thermostat works fine and just the gauge is misleading?

I had a CX-5 as a loaner with the same engine but I didn't do any measurements on that one (I was almost sure that the thermostat would solve my issue).
 

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The coolant valve part number from the factory for both of our CX-5 is also PYFD1516Z. The mystery right now is what that PYFD1516ZA number is all about.

The only 'testing' of the valve that they can do is to check to see if the ECT temp is where it should be. (unless Mazda has recently provided some additional testing of the valve that doesn't appear in the FSM)
 

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I edited my previous post; the new part starts with PYFD-* which is what they put on my car.


 

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... I wonder if it's a bad ECT sensor and maybe the thermostat works fine and just the gauge is misleading? ...
There are actually 2 ECTs installed on the CX-5, and I would expect that to be the case for your 3 as well. The other ECT (called ECT2) is not available via the basic OBD data, but it does appear in the Mazda proprietary data via their advanced OBD tool. So if either ECT was giving bad readings, it would immediately be apparent to them, because those 2 sensors should always be reading within a very small difference of each other.
 

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I'm very familiar with this whole thing, as a result of CX-5 owners posting the same issue on those forums, and both the CX-5 and the 3 have the identical control valve installed. And there are a couple of particularly troublesome aspects about this coolant valve problem. The first big problem is that there are no testing specs currently provided for the coolant valve in the FSM, which means that the ECT temp, or an OBD code is the only way to know that something might be wrong with the valve. However, there's currently no way to do any testing to confirm the valve is malfunctioning. Mazda is telling the stealerships to just hang on a new part, which IMO is a really weak effort on their part.
The service manual indicates that there is a position sensor on the valve. If there is a PID or if its monitored in any way by the ECU you would be able to see when it opens. Analog temperature measurements (not relying on the ECU to provide data) would then tell you if its working right, assuming of course the position sensor is accurate....

And, dovetailing with the first concern, is the fact that Mazda has provided no indication of what the problem with the valve is. There are three main components (actuator, sensor, and thermostat), and it's anyone's guess as to which one of them is causing the low coolant temps, or high temps for that matter as well.
This only goes to show how reliant the techs are on the digital information from the ECU / PCM and the service procedures provided by Mazda, and how little actual mechanical ability it takes to be a tech in the modern car world. It shouldn't take a competent person with decent mechanical ability very long to figure out how to bench-test a simple electronically controlled valve for functionality....and for that matter, it may not even be an issue with the valve itself, but rather a flaw in the PCM software that is keeping the valve open.....
 

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The service manual indicates that there is a position sensor on the valve. If there is a PID or if its monitored in any way by the ECU you would be able to see when it opens. Analog temperature measurements (not relying on the ECU to provide data) would then tell you if its working right, assuming of course the position sensor is accurate....
What you wrote is all true, however there is nothing in the FSM for my CX-5 about any testing of the coolant valve. So even if Mazda did assign a PID to this sensor voltage, it's of no use if they don't release that information and provide access to it via their proprietary scan tool. Perhaps they will do this in the future, but nothing yet as of today.


....This only goes to show how reliant the techs are on the digital information from the ECU / PCM and the service procedures provided by Mazda, and how little actual mechanical ability it takes to be a tech in the modern car world. It shouldn't take a competent person with decent mechanical ability very long to figure out how to bench-test a simple electronically controlled valve for functionality....and for that matter, it may not even be an issue with the valve itself, but rather a flaw in the PCM software that is keeping the valve open.....
Although I agree with you about the knowledge and skill level of the typical automaker service department, I have to say that IMO this coolant valve is quite a bit more complex than one would expect it to be. The ECM drives variable 3-way coolant flow, presumably via a combination of one or more flaps driven by the actuator, and using feedback from the position sensor.

Now all of that stuff is probably typical of how most of these things are designed, but (according to the documentation), this Mazda coolant valve also contains a mechanical thermostat squirreled away inside the case. So I believe it would be extremely difficult for anyone who has no specs, to be able to figure out how all of those 3 components are working together in synch, and even more difficult determining how to test all of it. The combination of 3 electrical points of failure (ECM, actuator and sensor), along with at least 2 non-electrical ones (mechanical t-stat, and flaps that might malfunction) seems like a mighty tall order for anyone to figure out how to diagnose, particularly when most of this stuff is locked away inside the case. But I suppose almost anything is possible to do, if enough time and effort is put into it.

Personally, I would trade this entire coolant valve $hit box for a good old, simple $10 mechanical t-stat, just like the ones on all of the other dinosaur vehicles that I've owned in the past.
 
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Talked with Mazda dealership and they got an answer from Mazda last Friday. They say they forgot to do a software update which was part of that TSB as a "counter measure" for something that I didn't quite get.
I do not see a software update in the TSB's listed in this topic but tomorrow morning I'm scheduled to do the software update and I'll provide an update after that.
 

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Talked with Mazda dealership and they got an answer from Mazda last Friday. They say they forgot to do a software update which was part of that TSB as a "counter measure" for something that I didn't quite get.
I do not see a software update in the TSB's listed in this topic but tomorrow morning I'm scheduled to do the software update and I'll provide an update after that.
That explanation does sound puzzling. The only thing that comes to mind is that it's some type of new part 'learning' process by the ECM, that it cannot do on its own. Hopefully you can find someone who is owner-friendly, and will provide some good information about this update, including where they are finding it and what the Mazda update number is.
 
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They did the software change and it seems to be better but temperature still dropping when driving on the highway. I wasn't able to get any more details into what they changed and I got no paperwork for it.
They went into saying due to cylinder deactivation the temperature drops when it doesn't have load.
This is how the gauge looks like after 20 miles of driving (90% highway).
My car will be sold within a year (before my warranty expire) as I don't wanna waste any more time.
Speedometer Car Vehicle Odometer Tachometer
A quick new measurement going on the highway and some backroads after 20 miles of driving already (when the engine should be fully warmed up already).
281397

This is how ti compares with my last measurement and it does seems better however the car was already running now for 20 miles before doing this measurement.
281399
 
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....
They went into saying due to cylinder deactivation the temperature drops when it doesn't have load.
....
They should have been able to come with better BS than that. The whole purpose for replacing the mechanical thermostat with an electronic control valves is to be able to adjust instantly to whatever operating conditions exist, and keep the coolant at basically a constant temp. And given that the ECM controls both CD, as well as the coolant control valve, adjusting the valve for anything related to CD would be a piece of cake. No need to even get into how insignificant the percentage of engine runtime with cylinders deactivated actually is. Typical stealership mumbo jumbo, when they don't have a clue.

Even though ECT temps are better than before, IMO they are still way too low, even at the highest point. As I posted previously, my CX-5 has a target coolant temp around 195F, and it stays there consistently. I don't have the specs for your vehicle, but suspect they can't be all that different from mine, given that they have the same engine installed.

But I certainly understand that you have no interest in continuing this frustrating effort, given that you will be dumping the vehicle in a year. So thanks for what you've reported here, and I'm guessing that it may very well turn out to be useful information, as more becomes known about these coolant valve issues.
 
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This is how the gauge looks like after 20 miles of driving (90% highway).
View attachment 281393
That's exactly how mine looks. Mine never gets warmer than that, and doesn't take that long to get warmed up to there either. Are you suggesting that because it's below the mid-line, it's not working properly?
 

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It climbs more than that during acceleration or uphill and drops when driving constant.

I had a 60 miles drive today at 68F and 90% of the time is normal as before and just dropping during engine brake/downhill as in the photo above.

So whatever software update they did yesterday, it helped but still not as before.

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The coolant valve part number from the factory for both of our CX-5 is also PYFD1516Z. The mystery right now is what that PYFD1516ZA number is all about.
They issued another bulletin on 03/08/2021 where the part is changed to PYFD-15-16Z (what I have on my car).
 

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