Circuit Description
The engine coolant temperature (ECT) sensor is a variable resistor, that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. 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, which is a high temperature indication, DTC P0117 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage
Conditions for Running the DTC
| • | The engine run time is more than 10 seconds. |
| OR |
| The engine run time is less than 10 seconds when the intake air temperature (IAT) is less than 50°C (122°F). |
| • | DTC P0117 runs continuously when the above condition is met. |
Conditions for Setting the DTC
The PCM detects that the ECT Sensor parameter is more than 138°C (280°F) for more than 23 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
| • | An overheating condition may cause this DTC to set. |
| • | If the condition is suspected of being an intermittent, refer to Testing for Intermittent Conditions and Poor Connections . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 | Observe the Engine Coolant Temperature (ECT) Sensor parameter with a scan tool. Is the ECT Sensor parameter more than the specified value? | 138°C (280°F) | Go to Step 4 | Go to Step 3 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Is the ECT Sensor parameter less than the specified value? | -38°C (-36°F) | Go to Step 6 | Go to Step 5 |
5 | Test the signal circuit of the ECT sensor for a short to ground or a short to the ECT low reference circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
6 | Test for an intermittent and for a poor connection at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
7 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
8 | Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
9 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 11 |
11 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
