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Q: Service engine light came on.

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Took the car to Auto Zone it read P 0128 coolant temperature low. I watch the gauges and it is usually at the first 1/4 mark on the temp. I have had trouble with the heater not blowing warm and the temp. dial not going above 65 degrees although sometimes it will turn to 90. Service engine light went off for a few days by itself but came back on again. The thermostat is very hard to change on this model. Do you think it could be the ect sensor or the thermostat?

My car has 155000 miles.
My car has an automatic transmission.

Hello, this code represents a slow acting thermostat getting to engine operating temperature which is about 195 degrees. The computer monitors the time to get to operating temperature, if it takes too long it will set this code. The issue could be the thermostat opening to quickly to circulate engine coolant. Low coolant level would also give this concern, that would mean the system has a leak. This would cause a cool operating and less heat to passenger compartment. The control panel for temperature would be a different concern. If you’d like, a certified Your Mechanic Technician can come to your location and inspect this condition. Please look at this web site for more information and service options. thermostat/low heat

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