Originally Posted by
Explicit_Spade
When the coolant is too low to effectively protect the internal temperature of the engine, the engine coolant temperature (ECT) sensor will provide a false reading to the powertrain control module (PCM). Once the PCM detects the anomaly in the coolant system, the ECT fails to communicate the necessary voltage signal from the PCM, which turns on the "check engine" light.
If the ECT is bad, you will need to replace it for the check engine light to clear. You can have the code manually cleared, and see if it comes back.