DTC P0128: Engine Coolant Fails To Reach Preset Target Temperature: Description

Engine Coolant Temperature (ECT) sensor monitors temperature of coolant. This input is used by PCM for engine control and as an enabling criteria for some diagnostics.

The airflow coming into engine is accumulated and used to determine if engine has been driven within conditions that would allow engine coolant to heat up normally to thermostat regulating temperature. If coolant temperature does not increase normally or does not reach regulating temperature of the thermostat, diagnostics that use engine coolant temperature as enabling criteria may not run when expected.

DTC will set when engine coolant fails to reach a preset target temperature before a calculated airflow is accumulated.