DTC P0125: General Description
The powertrain control module (PCM) supplies voltage to the engine coolant temperature signal circuit (about 5 V) through a pull-up resistor. As the engine coolant cools, the engine coolant temperature (ECT) sensor 1 resistance increases, and the PCM detects a high signal voltage. As the engine coolant warms, the ECT sensor 1 resistance decreases, and the PCM detects a low signal voltage. If the ECT sensor 1 output voltage does not reach a specified temperature at which closed loop control for stoichiometric air/fuel ratio starts within a set time, depending on the initial engine coolant temperature after starting the engine, the PCM detects a malfunction and stores a DTC.