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 P1114 sets.

#### DTC Descriptors

This diagnostic procedure supports the following DTC:

DTC P1114 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent Low Voltage

### Conditions for Running the DTC

• | The engine is running for more than 10 seconds.

| OR

• | The engine run time is less than 10 seconds when the intake air temperature (IAT) is less than 70°C (158°F).

### Conditions for Setting the DTC

The PCM detects that the ECT sensor parameter is more than 149°C (300°F) intermittently for more than 5 seconds.

### Action Taken When the DTC Sets

• | The control module stores the DTC information into memory when the diagnostic runs and fails.

• | The malfunction indicator lamp (MIL) will not illuminate.

• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

• | The driver information center, if equipped, may display a message.

### Conditions for Clearing the DTC

• | 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 non-emission related diagnostic.

• | Clear 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 Powertrain Control Module Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Observe the engine coolant temperature (ECT) sensor parameter with a scan tool. Is the ECT sensor parameter greater than the specified value? | 149°C (300°F) | Go to Step 4 | Go to Step 3
3 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 60 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Testing for Intermittent Conditions and Poor Connections

4 |

1. Disconnect the ECT sensor.
2. Observe the ECT sensor parameter with a scan tool.

Is the ECT sensor parameter less than the specified value?

-39°C (-38°F)

Go to Step 6

Go to Step 5

5 | Test the signal circuit of the ECT sensor for an intermittent short to ground or an intermittent short to the ECT low reference circuit. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7
6 | Test for an intermittent and for a poor connection at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8
7 | 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 to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9
8 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
9 | Replace the PCM. Refer to Control Module References . Did you complete the replacement? | -- | Go to Step 10 | --
10 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 60 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 11

11 | Observe the Capture Info with a scan tool. Have any other DTCs not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK