The wife’s 24’ CX5 2.5NA was throwing this code today. I do know that there is a TSB for this, it’s just going to be a matter of how long it’ll take for them to actually do it! Her coolant tank shows right on the “L” mark. When I remove the cap in order to try and top it off, there’s still coolant at the top of the cap. As a result it won’t take any coolant. She only has about 17k on the car.

 

Welcome to the forum

 

Sorry so what is the question?
As for the TSB post the number please.

As for any solution or starting to diagnosis the DTC which may not actually be within the TSB as many DTC can be several causes you are completely under warranty and as such should not do anything without consulting your Mazda dealership.
I would also strongly suggest not to attempt to do any service on your cooling system except to monitor the reservoir tank and should it go below the low level to fill it and check for sign of coolant leaking make note and record of it and then contact your dealership.

 

The TSB number is 01-005-23A
My main question is why I’m not able to add to the coolant tank. The level shows low, but when I remove the cap there is still coolant right under the cap.

 

Ya I thought that was the one. DIY and owners should not read TSB. If you read it there is a diagnosis process, first be done to determine several possible causes . This means a skilled and or Factory trained Mazda mechanic , or an employee with like or more certifications. Let your dealership service department handle your Mazda that is under warranty.

Your response makes no sense. If you remove the coolant tank cap and you see coolant right, there you are actually over the full limit. DONT ADD COOLANT.

 

Yes, it would appear nonsensical. I just found it odd that the reservoir reads on the “L”. Just seemed that there would be room to add.

 

If you can see it even if it is "L" then you are ok. Naturally the "F" would be full but if you are not leaking it then actually you would be surprised how many new off the dealership lots with ALL platforms that the coolant is at the "L" I could ex[plain why that it but it doesn't really help you. LOL


Mine would seem to be above full but in actually because I filled it with a cold engine and I just got home took this picture for your reference the fluid is always higher.

 

Did you ever get the letter for this code? I know about the TSB and what Callisto is saying about not interpreting a bulletin meant for techs but I actually got a letter from Mazda. It was notifying me of several model years including my old 2022 and my current 2025 being eligible for a 150,000 15 year warranty on the coolant control valve/thermostat and P0126 is the code. It explains everything and is meant to be customer facing. I lists the 2024 but I don't know if it is VIN specific. Either way get that thing to the dealer for service let them handle it!

 

You are under warranty take it to back to the dealer.
If you start messing it, you may find it voids your warranty.

 

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