For 1990-2009 cars

### 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.

### Conditions for Running the DTC

The engine is running.

### Conditions for Setting the DTC

• | The ECT sensor indicates an engine coolant temperature more than 140°C (283°F).

• | The above condition is present for more than 15 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.

After starting the engine, the ECT sensor temperature should rise steadily to about 90°C (194°F) then stabilize when the thermostat opens.

Use the Temperature vs. Resistance value table to test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns. Refer to Temperature Versus Resistance .

If the malfunction is not present at this time, refer to DTC P1114 .

If an intermittent condition is suspected, 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 | Go to Diagnostic System Check - Engine Controls
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Observe the ECT sensor temperature display.

Does the scan tool indicate that the ECT sensor temperature is greater than the specified value?

138°C (280°F)

Go to Step 4

Go to Step 3

3 |

1. Observe the Freeze Frame/Failure Records data for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC reset?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Disconnect the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, observe the ECT sensor temperature.

Does the scan tool indicate that the ECT sensor temperature is less than the specified value?

-38°C (-36°F)

Go to Step 6

Go to Step 5

5 |

1. Turn OFF the ignition.
2. Disconnect the PCM. Refer to Powertrain Control Module Replacement .
3. Test the signal circuit of the ECT sensor for a short to ground or a short to ECT reference low circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

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 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 9

Go to Step 2

9 | With a scan tool observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK