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 the 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, 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 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
| • | The engine is running. |
| • | DTCs P0101, P0102, P0103, P0112, P0113, P0116, P0117, P0118, P1111, P1112, P1114, or P1115 are not set. |
| • | The intake air temperature (IAT) is more than -40°C (-40°F). |
| • | The ECT is more than -40°C (-40°F). |
| • | The start-up ECT is 40°C (104°F) or less. |
Closed Loop Test
| • | Vehicle stabilized at -40°C (-40°F) |
| - | Accumulated air flow since start is more than 7 500 grams |
| - | Accumulated idle time is less than 360 seconds |
| • | Vehicle stabilized at -7°C (20°F) |
| - | Accumulated air flow since start is more than 4 500 grams |
| - | Accumulated idle time is less than 225 seconds |
| • | Vehicle stabilized at 10°C (50°F) |
| - | Accumulated air flow since start is more than 1 600 grams |
| - | Accumulated idle time is less than 90 seconds |
Conditions for Setting the DTC
| • | The Closed Loop coolant temperature is not reached within a predetermined time. The maximum allowable time depends upon the start up coolant temperature and the amount of airflow into the engine. |
| • | Vehicle stabilized at -40°C (-40°F) |
| The ECT is less than 20°C (68°F) after 8 minutes. |
| • | Vehicle stabilized at -7° (20°F) |
| The ECT is less than 20°C (68°F) after 5 minutes. |
| • | Vehicle stabilized at 10°C (50°F) |
| The ECT is less than 20°C (68°F) after 2 minutes. |
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. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
DTC P0125 is designed to detect a skewed ECT sensor or a faulty thermostat.
Excessive coolant flow through the bypass hose to the throttle body may cause this DTC to set.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for excessive resistance in the ECT circuit.
-
This step tests for a skewed sensor through the range of temperatures affecting this DTC.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 | Is the cooling system low on coolant? | -- | Go to Step 3 | |
Does scan tool indicate that the ECT sensor temperature is more than the specified value? | 138°C (280°F) | Go to Step 7 | Go to Step 4 | |
4 |
Does the scan tool indicate that the ECT sensor temperature is more than the specified value? | 138°C (280°F) | Go to Step 5 | Go to Step 6 |
5 |
Did you find and correct the condition? | -- | Go to Step 10 | -- |
6 |
Did you find and correct the condition? | -- | Go to Step 10 | -- |
Does the resistance and temperature closely match the Temperature vs. Resistance Table? | 10-90°C (50-194°F) | Go to Step 8 | Go to Step 9 | |
8 | Reinstall the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the action complete? | -- | Go to Thermostat Diagnosis in Engine Cooling | -- |
9 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC run and pass? | -- | Go to Step 11 | Go to Step 2 |
11 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
