Resetting of CEL on 2007 Mazda 3

Asked by Dec 20, 2013 at 10:51 AM about the 2007 Mazda MAZDA3 i Sport

Question type: Maintenance & Repair

I had a CEL on my 2007 Mazda 3,  2.0L and the code was P0128. I was told to change the thermostat. Now that it has been done the CEL is still there.
How long after the problem is fixed that the CEL goes away. Thanks

6 Answers


It should have gone away, so it must be something else. Maybe your ECT or IAT sensor is faulty. You will have to do some diagnostic work if you don't want to just replace parts. Here is that link that will help understand what P0128 means....

1 of 1 people found this helpful.

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?


Probably related since it's temperature dependent.


You may find this article helpful as well:


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.

2 of 2 people found this helpful.

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

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