Circuit Description
An engine coolant temperature (ECT) sensor monitors the temperature of the coolant. This input is used by the engine control module (ECM) for engine control and as an enabling criteria for some diagnostics.
The air flow into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to the Closed Loop temperature. If the coolant temperature does not increase normally or does not reach the Closed Loop temperature, the diagnostics that use engine coolant temperature as enabling criteria may not run when expected.
This DTC will only run once per ignition cycle within the enabling conditions.
If the ECM detects the calibrated amount of air flow and engine run time have been met, and the engine coolant has not met the Closed Loop temperature, DTC P0125 sets.
Conditions for Running the DTC
| • | The engine is running. |
| • | The start-up ECT is less than 14°C (57°F). |
Conditions for Setting the DTC
| • | The calibrated amount of air flow has been met. |
| • | The calibrated amount of engine run time has been met. |
| • | The minimum ECT for Closed Loop of 37°C (99°F) has not been met. |
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. |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
2 |
Important: The cooling fans are commanded ON when certain engine coolant temperature (ECT) DTCs are set. Is the cooling system coolant low? | -- | Go to Cooling System Draining and Filling in Engine Cooling | Go to Step 3 | ||||||
3 | Test and verify the proper operation of the thermostat. Refer to Thermostat Diagnosis in Engine Cooling. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 4 | ||||||
4 |
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 5 | ||||||
5 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 6 | ||||||
6 | Measure the resistance of the ECT sensor signal circuit between the sensor and the ECM with a DMM. Refer to Circuit Testing in Wiring Systems. Is the resistance within the specified range? | 0-10 ohms | Go to Step 7 | Go to Step 10 | ||||||
7 | Measure the resistance of the ECT sensor low reference circuit between the sensor and the ECM with a DMM. Refer to Circuit Testing in Wiring Systems. Is the resistance within the specified range? | 0-10 ohms | Go to Step 8 | Go to Step 11 | ||||||
8 |
Is the resistance measurement of the ECT sensor within the specified range? | -- | Go to Step 9 | Go to Step 12 | ||||||
9 | Install the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the action complete? | -- | Go to Step 13 | -- | ||||||
10 | Repair the high resistance in the ECT sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Did yo complete the repair? | -- | Go to Step 14 | -- | ||||||
11 | Repair the high resistance in the ECT sensor low reference circuit. Refer to Wiring Repairs in Wiring Systems. Did yo complete the repair? | -- | Go to Step 14 | -- | ||||||
12 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||||
13 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | Go to Step 14 | -- | |||||||
14 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 15 | ||||||
15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
