Causes and Fixes P0128 Code: Coolant Temperature Below Thermostat Regulating Temperature

How to fix P0128 Code: Coolant Temperature Below Thermostat Regulating Temperature
The computer (ECM/PCM) expects the engine coolant to reach a minimum operating temperature, around 160–190°F, depending on the vehicle, within a set time after startup, typically a few minutes, based on driving conditions, engine load, and ambient temperature.
When the expected engine temperature is not reached within a set time, a P0128 Code is set.

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The engine coolant temperature (ECT) sensor is a Thermistor, which is a resistor whose resistance changes with the temperature.

Possible Causes of a P0128 Code:
Low Engine Coolant Level
Bad Engine Coolant Temperature Sensor (ECT)
Bad Engine Thermostat

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