Circuit/System Description

The engine control module (ECM) monitors the temperature of the engine coolant for engine control and as enabling criteria for some diagnostics. The ECM monitors the amount of time to reach a predetermined temperature based on the Start up ECT sensor. The ECM uses this temperature to determine if the engine has warmed up to the thermostat regulating temperature. If the engine coolant temperature does not increase normally or does not reach the thermostat regulating temperature, diagnostics that use the ECT as enabling criteria, may not run when expected. If the engine coolant temperature fails to reach the thermostat regulating temperature, before a predetermined amount of time, the DTC sets.