Circuit Description
An engine coolant temperature (ECT) sensor monitors the coolant temperature. The powertrain control module (PCM) uses this input for engine control, and for an enabling criteria for some diagnostics.
The air flow coming into the engine is accumulated. The air flow is used in order to determine if the engine has been driven within conditions that would allow the engine coolant to heat normally to the thermostat-regulating temperature. If the coolant temperature does not increase normally, or if the coolant temperature does not reach regulating temperature of the thermostat, diagnostics that use engine coolant temperature as 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 Closed Loop fuel control.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0325, P0335, P0336, P0420, P0440, P0442, P0446, P0452, P0453, P0480, P0502 and P0503 for automatic transmission only, P0601, P0602, P0604, P0606, P1120, P1220, P1221, P1271, P1275, P1280, P1281, P1441, P1481, P1482, P1484, P1512, P1514, P1515, P1621, P1635, and P1639 are not set. |
| • | The engine has run more than 30 seconds and for less than 20 minutes. |
| • | The minimum intake air temperature (IAT) is more than -7°C (19°F). |
| • | The engine coolant temperature at start up is less than 40°C (104°F). |
Conditions for Setting the DTC
| • | The average air flow is more than 20 g/s. |
| • | The vehicle has traveled more than 0.8 km (0.5 mi) over 40 km/h (25 mph). |
| • | Enough air flow has entered the engine and the engine coolant temperature has not risen to 40°C (104°F) for 60 seconds. |
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. |
| • | A skewed IAT sensor may cause this DTC to set. The IAT sensor should read near ambient temperature. |
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 Loss of Coolant in Engine Cooling | Go to Step 3 |
Does the 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 | |
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 | -- |
7 |
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 | Install 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 | Observe the stored information, Capture Info., with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
