DTC P0125: Engine Coolant Temperature (ECT) Sensor Malfunction/Slow Response: General Description
The engine control module (ECM) supplies voltage to the engine coolant temperature (ECT) signal circuit (about 5 V) through a pull-up resistor. As the engine coolant cools, the ECT sensor resistance increases, and the ECM detects a high signal voltage. As the engine coolant warms, the ECT sensor resistance decreases, and the ECM detects a low signal voltage.
If the ECT 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 coolant temperature after starting the engine, the ECM detects a malfunction and a DTC is stored.
MONITOR DESCRIPTION CHART
| Execution | Once per driving cycle |
| Sequence | None |
| Duration | 20 minutes or less |
| DTC Type | Two drive cycles, MIL ON |
ENABLE CONDITIONS CHART
| Condition | Minimum | Maximum |
|---|---|---|
| Initial engine coolant temperature | - | 14°F (-10°C) |
| Fuel feedback | Other than during fuel cut-off operation | |
| No active DTCs | A/F Sensor, A/F Sensor Heater, MAP, CKP, CMP, ECT, IAT, BARO, IAC, EGR, EVAP, VTEC System, Fuel System, Misfire | |