Circuit Description
The controls module monitors the engine coolant temperature (ECT) sensor and engine run time in order to determine how long it takes the ECT to reach the coolant temperature required for Closed Loop operation. DTC P0125 sets if the control module determines that the ECT does not reach a minimum coolant temperature required for Closed Loop operation in a specified amount of time.
Conditions for Running the DTC
| • | The engine is running |
| • | No active ECT sensor DTCs |
| • | No active IAT sensor DTCs |
| • | The IAT is greater than -40°C(-40°F) |
| • | The ECT is greater than -40°C(-40°F) |
| • | The start-up ECT is less than 40°C(-40°F) or less |
Closed Loop Test
| • | Vehicle stabilized at -40°C(-40°F) |
| - | Accumulated air flow since start is greater than 7,500 grams |
| - | Accumulated idle time is less than 300 seconds |
| • | Vehicle stabilized at -7°C(20°F) |
| - | Accumulated air flow since start is greater 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 greater 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 on the start-up coolant temperature and the amount of air flow into the engine. |
| • | Vehicle stabilized at -40°C(-40°F) |
| ECT less than 20°C(68°F) after 8 minutes |
| • | Vehicle stabilized at -7°C(20°F) |
| ECT less than 20°C(68°F) after 5 minutes |
| • | Vehicle stabilized at 10°C(50°F) |
| ECT less than 20°C(68°F) after 2 minutes |
Action Taken When the DTC Sets
The VCM turns the MIL ON after 2 consecutive driving cycles with the fault active.
Conditions for Clearing the MIL/DTC
The VCM turns OFF the MIL after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle) or the scan tool clearing feature has been used.
Diagnostic Aids
When a DTC P0125 sets, a skewed ECT sensor or the engine thermostat that does not operate correctly is indicated.
A poor connection, a rubbed through wire insulation, or a wire broken inside of the insulation may cause an intermittent.
Check for the following conditions:
| • | A poor connection or a damaged harness. Inspect the VCM harness connector for the following conditions: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal to wire connection and |
| - | A damaged harness |
| • | The intermittent test: If the connections and the harness check OK, monitor a digital voltmeter connected between the VCM terminals while moving the related connectors and the wiring harness. If the failure is induced, the voltage reading changes. This may help in order to isolate the location of the malfunction. |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
This test checks the engine warm-up rate. In the Conditions for Setting the DTC text, the technician should be able to reference the allowable engine run time relative to the cold start up temperature of the vehicle.
-
This test checks the coolant sensor reading on the scan tool and the actual coolant temperature.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear DTC Information function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 |
Is the IAT and the ECT near the same temperature? | -- | Go to DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage | |
Operate the vehicle within the conditions for setting this DTC as specified in the Conditions for Setting the DTC text. Does the ECT value rise steadily to and above the specified value within the time and temperature specified in the supporting text? | 20°C (68°F) | Go to Diagnostic Aids | ||
4 |
Is the coolant level low? | -- | Go to Engine Cooling System | |
Compare the ECT display on the scan tool to the actual coolant temperature. Is the actual coolant temperature near the scan tool ECT? | -- | Go to Engine Cooling System | ||
6 |
Is the voltage above the specified value? | 4.0V | ||
7 | Check the ECT sensor signal circuit between the VCM and the ECT sensor connector for a short to ground. Was a problem found? | -- | ||
8 | Repair the circuit as necessary. Refer to Wiring Repairs in Repair Instructions. Is the action complete? | -- | -- | |
9 | Check the ECT sensor electrical connector for a poor connection and repair as necessary. Refer to Wiring Repairs in Repair Instructions. Was a problem found? | -- | ||
10 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement in Repair Instructions. Is the replacement complete? | -- | -- | |
11 | Check the VCM connectors for a poor connection and repair as necessary. Refer to Wiring Repairs in Repair Instructions. Was a problem found? | -- | ||
12 |
Is the action complete? | -- | -- | |
13 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
14 | Use the scan tool in order to display the Capture Info and the Review Capture Info functions. Are there any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
