Resetting of CEL on 2007 Mazda 3

Thanks Tom So based on the info in your link: Low engine coolant level (Checked Good) Leaking or stuck open thermostat (New Thermostat Installed) Faulty cooling fan (running too much) (Not the case here) Faulty coolant temperature (ECT) sensor - POSSIBLE Faulty intake air temperature (IAT) sensor - POSSIBLE So I have to check the 2 sensors. One thing to note is that the CEL goes away in the summer time (talking about Arizona), and came back in the winter time. Does that indicate some other issue?

You may find this article helpful as well: http://repairpal.com/OBD-II-Code-P0128

Did you ever figure this out? I am currently in the same bind you were in. Changed the thermo and engine coolant temp sensor but the light is still on.

I'm willing to bet the code is still stored in the computer. Unless someone actually cleared the CEL from the computer after the repair, the CEL light won't go out. You have to clear the code and drive the car for XXX miles for the computer to reset itself. If the repair was done, the code was cleared, and computer reset, and still have the CEL light, you may have a different problem