P0126

Insufficietn coolant temp for stable operation. What usually needs to be replaced here? Thanks!

It is typically related to the thermostat, sometimes being stuck open, and allowing the coolant temp to drop too low.

For what it is worth, and perhaps might apply to your scenario, I also received this code twice as a false positive when I did a very long coast down hill for many miles, without any throttle, while coming down from the mountain peak. I was able to reset the ECU and it never reappeared.

There is some good info in this thread... https://www.mazdas247.com/forum/showthread.php?123835119-P0126-Thermostat-or-Sensor/page2
 
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Yes thats exactly when the CEL appeared during a long drive in the mountains with a lot of downhill! Would replacing the thermostat be the safer thing to do? I just dont want the CEL coming on again
 
Yes thats exactly when the CEL appeared during a long drive in the mountains with a lot of downhill! Would replacing the thermostat be the safer thing to do? I just dont want the CEL coming on again

LOL that is awesome..., if it were mine, I would RESET the code. If it appears again shortly, you will then know it is indeed a problem, and not a false downhill triggered code.
 
LOL that is awesome..., if it were mine, I would RESET the code. If it appears again shortly, you will then know it is indeed a problem, and not a false downhill triggered code.

I reset the code and after 150 miles the CEL has not come back. I guess it was triggered by the downhill drive. Thank you!
 
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