DTC P0125: ECT Excessive Time To Enter Closed Loop Fuel Control: Description

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

The Engine Coolant Temperature (ECT) sensor is a thermistor. The ECT thermistor has high resistance when cold and low resistance when hot. The Powertrain Control Module (PCM) supplies about 5 volts on the ECT signal circuit. The PCM also supplies a ground circuit to the ECT sensor. When ECT resistance is high (cold sensor), the ECT signal voltage remains near the supplied 5 volts. As the ECT sensor warms and resistance drops, more signal circuit voltage is pulled lower to the sensor ground. The PCM and the Alternative Fuels Engine Control Module (AF ECM) monitor the ECT signal circuit voltage in order to determine the engines temperature.

This DTC is used to indicate an engine coolant temperature that is less than the temperature necessary to enable AF ECM Closed Loop fuel control.