Circuit Description
The engine coolant temperature (ECT) sensor is a thermistor. A thermistor is a resistor whose value varies with temperature. The ECT sensors resistance is high when the coolant temperature is cold, and the ECT sensors 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
| • | The engine coolant temperature is less than -6.7°C (20°F) at engine start up. |
| • | The ECT sensor value is 35°C (95°F) or less after the engine has been running for 20 minutes or more. |
OR:
| • | The engine coolant temperature is between -6.7°C and +10°C (20°F and 50°F) at engine start up. |
| • | The ECT sensor value is 35°C (95°F) or less after the engine has been running for 5 minutes or more. |
OR:
| • | The engine coolant temperature is more than 10°C (50°F) at engine start up. |
| • | The 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
| • | The engine coolant temperature or the intake air temperature (IAT) sensor value is less than -6.7°C (20°F) at engine start up. |
| • | The ECT sensor value is 35°C (95°F) or less after the engine has been running for 20 minutes or more. |
OR:
| • | The engine coolant temperature is between -6.7°C and 10°C (20°F and 50°F) or the ambient air temperature is between -6.7°C and 10°C (20°F and 50°F) at engine start up. |
| • | The ECT sensor value is 35°C (95°F) or less after the engine has been running for 5 minutes or more. |
OR:
| • | The engine coolant temperature is more than 10°C (50°F) or the ambient air temperature is more than 10°C (50°F) at engine start up. |
| • | The 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 2 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 3 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 engines cooling system, including the correct coolant level. |
| • | A faulty thermostat that stays open slightly can cause 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 ECT sensor. A shifted sensor could result in 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:
| • | Any backed-out terminals |
| • | Any improper mating of terminals |
| • | Any broken electrical connectors locks |
| • | Any improperly formed or damaged terminals |
| • | Any faulty terminal-to-wire connections |
| • | Any physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Any corrosion of the electrical connections, the splices, or the terminals |
Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems.
If 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.
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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.
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This step checks for a faulty ECT sensor or ECT sensor circuit.
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This step checks the integrity of the ECT sensor input circuit.
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This step checks the integrity of the ECT sensor ground circuit.
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This step checks the integrity of the ECT sensor input circuit.
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A cooling system that prevents the engine from warming up properly and reaching the correct engine operating temperature within a set run time 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 .
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This step determines if DTC P0116 is the result of a hard failure or an intermittent condition.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||||
2 | Check for DTC P0115 with a scan tool. Is DTC P0115 set? | -- | Go to DTC P0115 Engine Coolant Temperature (ECT) Sensor Circuit | |||||||||
Is the ECT sensor value displayed near the actual coolant temperature? | -- | |||||||||||
Does the engine coolant temperature equal the specified value? | -40 C (-40°F) | |||||||||||
Does the engine coolant temperature equal the specified value? | 140°C (284°F) | |||||||||||
Does the engine coolant temperature equal the specified value? | 140°C (284°F) | |||||||||||
7 | Repair the open or incorrect resistance in the ECT sensor ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | ||||||||||
8 |
Was a repair necessary? | -- | ||||||||||
9 |
Was a repair necessary? | -- | ||||||||||
10 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |||||||||
Was a repair necessary? | -- | |||||||||||
Does DTC P0116 set? | -- | Go to Diagnostic Aids | ||||||||||
13 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the action complete? | -- | -- | |||||||||
14 |
Are any DTCs displayed on scan tool? | -- | System OK |
