P0125

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor monitors the temperature of the coolant. This input is used by the Powertrain Control Module (PCM) for engine control and as an enabling criterion for some diagnostics.

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

This DTC will only run once per ignition cycle within the enabling conditions.

This DTC will set when excess time is necessary in order to reach a minimum coolant temperature required for Closed Loop fuel control.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0110, P0111, P0112, P0113, P0117, P0118, P1114, and P1115 are not set.
^ The minimum Intake Air Temperature (IAT) is more than -7°C (19°F).
^ The ECT at start up is less than 50°C (122°F).
^ The ECT at start up is more than -40°C (-40°F).

CONDITIONS FOR SETTING THE DTC
An excessive amount of time passes before the ECT reaches the Closed Loop operation 10°C (50°F) threshold. The amount of time ranges between 2 and 13 minutes depending on the ECT at start up and the amount of air cycled through the engine since start up.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) if a failure is detected during 2 consecutive key cycles.
^ The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records.

CONDITIONS FOR CLEARING THE MIL OR DTC
^ The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed.
^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle.
^ Use a scan tool in order to clear the DTCs.

DIAGNOSTIC AIDS
A DTC P0125 is designed to detect a skewed ECT sensor or a faulty thermostat.

A skewed IAT sensor may cause this DTC to set. The IAT sensor should read near the ambient temperature while driving.

TEST DESCRIPTION

Steps 1-3:

Steps 4-11:

The numbers below refer to the step numbers on the diagnostic table.
3. This step tests for excess resistance in the ECT circuit.
4. This step tests for a skewed sensor through the range of temperatures affecting this DTC.