NHTSA Complaint #11566864 — 2019 MAZDA MAZDA3

The engine coolant system/electronic coolant control valve is known for failing on the N/A Skyactiv-G engine. When it fails, it fails stuck open. There is a TSB out for this problem (01-011/21). This results in the engine coolant never making it to operating temperature, and poor heater performance during cold weather. When I took it to a dealer, they stated that the check engine light must come on from DTC P0126:00 before they can address the problem under warranty. Even after driving the car and having 30+ minute drives where the temperature gauge never makes it past the first tick (blue), I haven't had the check engine light come on. It's unclear what circumstances are required for DTC P0126:00 to occur, but I've never had a car essentially not get warm during an entire 30+ mile highway drive, even when it's 0 fahrenheit outside. It appears like this is a degenerative problem as I did not have this problem last cold season. This year, since the first day it has been colder than about 45 degrees, the engine has struggled to reach operating temperature, and of course is even worse now that it is colder. Without the heated seat, it would be difficult to be comfortable in this car due to this problem.