2019 Mazda Mazda3 — costs that mattered more than fuel economy

I wouldn't throw parts yet. Swap the cheap/easy piece first on the 2019 Mazda Mazda3 and see if the fault moves. If the cheap test changes it, stop and reassess. No need to make it theatrical. If it repeats twice more I'll book time.

If it were in my driveway, a pressure test beats staring at a dry driveway if the 2019 Mazda Mazda3 is losing coolant with no puddle. Don't erase codes until someone who can help has seen them. That's the sequence I'd use. Next check is the cheap one I can do in a driveway.