For 1990-2009 cars
Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The engine coolant temperature (ECT) sensor uses a thermistor in order to control the signal voltage to the Powertrain Control Module (PCM). The PCM supplies a voltage on the signal circuit to the sensor. When the engine is cold, the sensor resistance is high and the ECT signal voltage will be high.

As the engine warms, the sensor resistance decreases and the voltage drops. At the normal engine operating temperature, the voltage will be between 1.5 and 2.0 volts at the ECT signal terminal.

The ECT sensor controls the following items:

• | The fuel delivery

• | The torque converter clutch (TCC)

• | The ignition control (IC)

• | The EVAP canister purge valve

• | The idle air control (IAC) valve

• | The electric cooling fan

### Conditions For Running The DTC

The engine run time is more than 60 seconds.

### Conditions for Setting the DTC

The ECT sensor indicates that the ECT is less than -40°C (-40°F) for 6.25 seconds.

### Action Taken When the DTC Sets

• | The Malfunction Indicator Lamp (MIL) will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.

• | A history DTC stores.

• | The coolant fan turns on.

• | The PCM will default to 20°C (68°F) for the first 60 seconds of the engine run time and then to 92°C (198°F).

### Conditions for Clearing the MIL/DTC

• | The MIL will turn off after 3 consecutive ignition cycles in which the diagnostic runs without a fault.

• | A history DTC will clear after 40 consecutive warm up cycles without a fault.

• | Use a scan tool to clear the DTCs.

### Diagnostic Aids

• | The normal operating temperature for the engine cooling system is between 90°C and 95°C (194°F- 203°F).

• | Use the Temperature vs. Resistance table in order to evaluate the possibility of a skewed sensor. Refer to Temperature Versus Resistance .

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step simulates a DTC P0117. If the PCM senses the change, then the PCM and the ECT wiring are OK.

2. The replacement PCM must be reprogrammed and the Crankshaft Position System Variation Learn procedure must be preformed.

#### DTC P0118-Engine Coolant Temperature (ECT) Circuit-High Voltage

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Turn on the ignition, leaving the engine off. Is the ECT less than the specified value? | -30°C (-22°F) | Go to Step 4 | Go to Step 3
3 |

1. Review and record the Freeze Frame data.
2. Operate the engine within the Freeze Frame conditions and the Conditions for Running the DTC, as specified in the supporting text.

Is the ECT s less than the specified value?

-30°C (-22°F)

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn off the ignition.
2. Disconnect the ECT sensor connector.
3. Connect a fused jumper between the ECT sensor signal circuit and ground circuit at the connector:
4. Turn on the ignition, leaving the engine off.

Is the ECT more than the specified value?

130°C (266°F)

Go to Step 6

Go to Step 5

5 | Connect a fused jumper between the ECT sensor signal circuit and ground at the connector . Is the ECT more than the specified value? | 130°C (266°F) | Go to Step 7 | Go to Step 8
6 |

1. Turn off the ignition.
2. Inspect for poor connections at the ECT sensor connector.
3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

7 |

1. Turn off the ignition.
2. Test for an open in the ECT sensor ground circuit.
3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

8 |

1. Turn off the ignition.
2. Test the ECT sensor signal circuit for the following conditions:

• | An open circuit

• | A short to voltage

3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

9 | Inspect for poor connections at the PCM. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11
10 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the repair? | -- | Go to Step 12 | --
11 | Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Step 12 | --
12 |

1. Use a scan tool to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK