Circuit Description
The engine coolant temperature (ECT) sensor is a thermistor, or variable resistor, that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the ECT signal circuit through a pull-up resistor. When the engine coolant temperature is cold, the sensor resistance is high. When the engine coolant temperature increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively low ECT signal voltage (a high temperature indication), this diagnostic trouble code (DTC) will set.
Conditions for Running the DTC
| • | DTCs P0112, P0113, P1111, or P1112 are not set. |
| • | The engine has been running for at least 10 seconds. |
| • | The intake air temperature (IAT) is less than 70°C (158°F). |
Conditions for Setting the DTC
| • | The ECT sensor temperature is more than 149°C (300°F) for longer than 10 seconds. |
| • | The condition exists for less than 1 second. |
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
For intermittent conditions, refer to Intermittent Conditions .
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 |
Does the scan tool indicate an engine coolant temperature more than the specified value? | 125°C (257°F) | Go to Step 4 | Go to Step 3 |
3 |
Does the scan tool indicate that DTC P0117 failed last test? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Does the scan tool indicate an engine coolant temperature near the specified value? | -40°C (-40°F) | Go to Step 6 | Go to Step 5 |
5 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 |
6 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
7 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Does the DTC run and pass? | -- | Go to Step 9 | Go to Step 2 |
9 | With a scan tool, observe the stored information in Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the Diagnostic Trouble Code (DTC) List | System OK |
