P0125

CIRCUIT DESCRIPTION
An 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 criteria for some diagnostics.

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

This Diagnostic Trouble Code (DTC) will only run once per ignition cycle within the enabling conditions.

This DTC will set when there has been excessive time to reach a minimum coolant temperature required for Closed Loop fuel control.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0100, P0101, P0103, P0110, P0111, P0112, P0113, P0117, P0118, P0125, P0500, P0501, P0503, P1114, or P1115 are not set.
^ The minimum intake air temperature is -7°C (+19°F) or more.
^ The start-up engine coolant temperature is less than 40°C (104°F).
^ The engine is running more than 2 minutes and less than 17 minutes.
^ The vehicle speed is more than 8 km/h (5 mph) for more than 0.8 km (0.5 miles).
^ The Mass Air Flow (MAF) average reading is more than 15 g/sec.

CONDITIONS FOR SETTING THE DTC
The Closed Loop engine coolant temperature of 40°C (104°F) is not reached within a predetermined time.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

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

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 excessive resistance in the ECT circuit.
7. This step tests for a skewed sensor through the range of temperatures affecting this DTC.