For 1990-2009 cars
Engine Controls Components
Cell 20:Engine Data Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The engine coolant temperature (ECT) sensor is a thermistor. A thermistor is a resistor whose value varies with temperature. The ECT sensor's resistance is high when the coolant temperature is cold, and the ECT sensor's resistance is low when the coolant temperature is warm. The ECT sensor is wired in series with a fixed resistor in the powertrain control module (PCM). The PCM applies 5 volts to the ECT sensor. The PCM monitors the voltage across the ECT sensor and converts the voltage into a temperature reading. The PCM will receive a high voltage input when the coolant temperature is cold. The PCM will receive a low voltage input when the coolant temperature is warm. A DTC P0116 may set if the ECT sensor voltage does not indicate that the engine coolant temperature has increased sufficiently during engine operation.

### Conditions for Running the DTC

• | Engine coolant temperature (ECT sensor value) is less than -6.7°C (20°F) at engine start up.

• | ECT sensor value is 35°C (95°F) or less after the engine has been running for 20 minutes or more.

OR

• | Engine coolant temperature (ECT sensor value) is between -6.7°C and 10°C (20°F and 50°F) at engine start up.

• | ECT sensor value is 35°C (95°F) or less after the engine has been running for 5 minutes or more.

OR

• | Engine coolant temperature (ECT sensor value) is more than 10°C (50°F) at engine start up.

• | ECT sensor value is 35°C (95°F) or less after the engine has been running for 2 minutes or more.

### Conditions for Setting the DTC

• | Engine coolant temperature (ECT sensor value) or the ambient air temperature (IAT sensor value) is less than -6.7°C (20°F) at engine start up.

• | ECT sensor value is 35°C (95°F) or less after the engine has been running for 20 minutes or more.

OR

• | Engine coolant temperature (ECT sensor value) is between -6.7°C and 10°C (20°F and 50°F) or the ambient air temperature (ECT sensor value) is between -6.7°C and 10°C (20°F and 50°F) at engine start up.

• | ECT sensor value is 35°C (95°F) or less after the engine has been running for 5 minutes or more.

OR

• | Engine coolant temperature (ECT sensor value) is more than 10°C (50°F) or the ambient air temperature (ECT sensor value) is more than 10°C (50°F) at engine start up.

• | ECT sensor value is 35°C (95°F) or less after the engine has been running for 2 minutes or more.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after three consecutively passing trips without a fault present.

• | A History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Use the scan tool Clear DTC Information function.

### Diagnostic Aids

Check for the following conditions:

• | If DTCs P0105, P0110, P0115, and P0120 are also set, the malfunction may be in a sensor ground circuit.

• | If DTCs P0115 and P0116 are both set the ECT sensor circuit may be open or shorted. Perform the DTC P0115 diagnostic table first.

• | Check for the proper operation of the engine's cooling system, including the correct coolant level.

• | A faulty thermostat that stays open slightly can cause a DTC P0116 to set in cold weather when the vehicle is started and let sit while warming up. Replace any suspect thermostat.

• | Use the Temperature vs Resistance table in order to evaluate the possibility of a shifted (incorrectly calibrated) ECT sensor. A shifted sensor could result in a DTC P0116. Refer to Temperature Versus Resistance .

• | Check for a faulty electrical connection to the PCM.

An intermittent malfunction may be caused by a fault in the ECT sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:

• | Backed out terminals.

• | Improper mating of terminals.

• | Broken electrical connectors locks.

• | Improperly formed or damaged terminals

• | Faulty terminal to wire connections.

• | Physical damage to the wiring harness.

• | A broken wire inside the insulation.

• | Corrosion of electrical connections, splices, or terminals.

Repair any electrical circuit faults that were found. Refer to Wiring Repairs .

If a DTC P0116 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks for a faulty ECT sensor or ECT sensor circuit.

3. This step checks the integrity of the ECT sensor input circuit.

4. This step checks the integrity of the ECT sensor ground circuit.

5. This step checks the integrity of the ECT sensor input circuit.

6. A cooling system that prevents the engine from warming up properly and reaching the correct engine operating temperature within a set runtime can cause a DTC P0116 to set. A thermostat that stays open slightly can cause a DTC P0116 to set in cold weather when the vehicle is started and let sit while warming up. Replace the thermostat if suspect .

7. This step determines if DTC P0116 is the result of a hard failure or an intermittent condition.

Step | Action | Value(s) | 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 | Check for a DTC P0115 with a scan tool. Is a DTC P0115 present? | -- | Go to DTC P0115 Engine Coolant Temperature (ECT) Sensor Circuit | Go to Step 3
3 |

1. Measure the actual coolant temperature.
2. Turn ON the ignition, leaving the engine OFF.
3. Observe the ECT sensor parameter on the scan tool.

Is the ECT sensor value displayed near the actual coolant temperature?

--

Go to Step 11

Go to Step 4

4 |

1. Disconnect the ECT sensor electrical connector.
2. Observe the ECT sensor parameter on the scan tool.

Does the scan tool indicate the specified value?

-40 C (-40°F)

Go to Step 5

Go to Step 8

5 |

1. Disconnect the ECT sensor electrical connector.
2. Jump the ECT sensor input circuit and the ground circuit together at the ECT sensor harness connector.
3. Observe the ECT sensor parameter on the scan tool.

Does the scan tool indicate the specified value?

140°C (284°F)

Go to Step 13

Go to Step 6

6 |

1. Jump the ECT sensor input circuit to chassis ground.
2. Observe the ECT sensor parameter on the scan tool.

Does the scan tool indicate the specified value?

140°C (284°F)

Go to Step 7

Go to Step 8

7 | Repair the open or electrical resistance in the ECT sensor ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 14 | Go to Step 9
8 |

1. Turn OFF the ignition.
2. Disconnect the PCM electrical connector C2.
3. Check the ECT sensor input circuit for a short or high electrical resistance.
4. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 14

Go to Step 9

9 |

1. Check for a faulty connection at the PCM and the ECT electrical connectors.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 14

Go to Step 10

10 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 14 | --
11 |

1. Inspect the engine cooling system for any of the following conditions:

• | Faulty thermostat, refer to Thermostat Diagnosis in Engine Cooling.

• | Low coolant level

• | Incorrect coolant

• | Faulty cooling system operation, refer to Engine Fails To Reach Normal Operating Temperature in Engine Cooling.

2. Repair as necessary. Refer to Engine Cooling.

Was a repair necessary?

--

Go to Step 14

Go to Step 12

12 |

1. Perform the scan tool Clear DTC Information function.
2. Place the vehicle into Check Mode, using the scan tool.
3. Operate the vehicle within the Freeze Frame conditions as specified.

Does a DTC P0116 set?

--

Go to Step 13

Fault Not Present-Go to Diagnostic Aids

13 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the action complete? | -- | Go to Step 14 | --
14 |

1. Perform the scan tool Clear DTC Information function and road the vehicle wihin the Freeze Frame conditions that set the DTC.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on scan tool?

--

Go to the Applicable DTC Table

System OK