Circuit Description
The powertrain control module (PCM) monitors the engine coolant temperature (ECT) sensor in order to determine how long it takes the engine to reach the coolant temperature required for Closed Loop operation. DTC P0125 sets if the PCM determines that the engine does not reach Closed Loop temperature in a specified amount of time. This test will not run if either the intake air or engine coolant temperature is too low at start-up.
Conditions for Running the DTC
| • | DTCs P0112, P0113, P0117, P0118 not set |
| • | The engine is operating. |
| • | The engine coolant temperature is between -36°C (-33°F) and +40°C (+104°F) at engine start-up. |
| • | The intake air temperature is more than -7°C (19°F). |
| • | The vehicle speed is more than 1.6 km/h (1 mph). |
Conditions for Setting the DTC
The Closed Loop coolant temperature of 34°C (93°F) is not reached within a predetermined time. The maximum allowable time depends on the start-up coolant temperature and the amount of airflow into the engine. The range for the time is from 2 minutes and 20 seconds to 22 minutes and 30 seconds.
Action Taken When the DTC Sets
| • | The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records. |
Conditions for Clearing the DTC
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Use a scan tool in order to clear the DTC. |
Diagnostic Aids
Important:
• Remove any debris from the PCM connector surfaces before servicing
the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the
PCM. Ensure that the gaskets are installed correctly. The gaskets prevent
contaminant intrusion into the PCM. • For any test that requires probing the PCM or component
harness connectors, use the J 35616
connector test adapter kit. Using this kit prevents
any damage to the harness connector terminals. Refer to
Using Connector Test Adapters
in Wiring
Systems.
| • | If the engine has sat overnight, the engine coolant temperature and intake air temperature values should display within a few degrees of each other. If the temperatures are not within 3°C (5°F), refer to Temperature vs Resistance . |
| • | If you determine that the DTC occurs intermittently, performing the P1114 or P1115 diagnostics table may isolate the cause of the fault. |
| • | An engine coolant temperature exceeding 34°C (93°F), indicates that the engine is capable of reaching the proper temperature, but not necessarily in the correct amount of time. Repeat this diagnostic table on a cold engine, and measure the time required to reach the temperature threshold. When starting a cold engine, measure the amount of time it takes the engine to reach the specified temperature. The engine should reach the specified temperature within 5 minutes or less. If the engine does not reach the specified temperature within 5 minutes, inspect for the following: |
| - | Coolant level -- Refer to Loss of Coolant. |
| - | Thermostat operation -- Refer to Thermostat Diagnosis. |
| - | Fans are on at all times -- Refer to Electric Cooling Fan Diagnosis. |
| - | Cooling system air pocket, system may need to be bled. Refer to Cooling System. |
| • | For an intermittent condition, refer to Symptoms . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
An ECT failure could cause a DTC P0125 to set, so correct any ECT diagnostic trouble codes that are set.
-
If it is obvious that the engine is not reaching full operating temperature, for example the radiator hoses never get very warm, or there is a concern of little or no heat from the heater, you can skip this step.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||
Are any engine coolant temperature DTCs set? | -- | Go to the applicable DTC table | ||||||||||
3 |
Does scan tool indicate the ECT sensor is less than the specified value? | -35°C (-31°F) | Go to DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage | |||||||||
4 | Jumper the terminals of the ECT sensor harness connector together using a jumper wire. Does the scan tool indicate the ECT is more than the specified value? | 139°C (282°F) | Go to DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage | |||||||||
5 |
Important: Allow the engine to warm up if it has not already reached the specified temperature. Five minutes is the maximum amount of time it should take to reach this temperature from a cold start. Less time is required if the engine is already warm. Does the scan tool indicate the engine coolant temperature reached the specified value? | 34°C (93°F) | Go to Diagnostic Aids. | |||||||||
Measure the resistance of the ECT sensor using a DMM. Refer to Temperature vs Resistance . Is the ECT resistance close to the value indicated in the Temperature vs Resistance table? | -- | |||||||||||
7 |
Is the action complete? | -- | -- | |||||||||
8 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the action complete? | -- | -- | |||||||||
9 |
Does the scan tool indicate that this test failed? | -- | ||||||||||
10 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
