DTC P0128: ECT Excessive Time To Reach Operating Temperature: Description

Engine Coolant Temperature (ECT) sensor monitors temperature of engine coolant. This input is used by Powertrain Control Module (PCM) for engine control and as an enabling criteria for some diagnostics. Airflow coming into the engine is accumulated and used to determine if engine has been driven within the conditions that would allow the engine coolant to heat to thermostat regulating temperature. If coolant temperature does not increase normally, or does not reach the regulating temperature, diagnostics that use ECT as an enabling criteria may not run properly.