All codes › P0128

P0128 — Engine Not Reaching Operating Temperature

P0128 is set when the engine fails to reach the calibrated minimum operating coolant temperature within a calibrated time and distance. The ECM monitors coolant temp, ambient temp, and time. If the engine never hits the temperature it should after driving long enough to warm up, the most likely cause is a thermostat stuck partially open — coolant is circulating to the radiator constantly instead of being blocked until the engine warms.

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