P0116

DTC P0116: Engine Coolant Temperature (ECT) Sensor Performance

Wiring Diagram:

Circuit Description
The DTC P0116 checks the accuracy of the ECT sensor signal. The ECT sensor is a thermistor. A thermistor is a resistor whose value varies with temperature. The ECT sensor resistance is high when the coolant temperature is cold, and the ECT sensor resistance is low when the coolant temperature is warm. The ECM applies 5 V to the ECT sensor. The ECM monitors the voltage across the ECT sensor and converts the voltage into a temperature reading. The ECM will receive a high voltage input when the coolant temperature is cold. The ECM 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 Setting the DTC

(Condition 1)
- Ignition ON with the engine running.
- Difference of the substitute coolant temperature values is higher than pre-determined value.
- Difference of the measured coolant temperature values is less than pre-determined value.

(Condition 2)
- Ignition ON with the engine running.
- Start-up coolant temperature is higher than 75.75 degrees C (168.4 degrees F).
- Start-up IAT is between -9.75 degrees C (14.45 degrees F) and 69.75 degrees C (157.6 degrees F).
- Ambient air temperature is higher than -9.75 degrees C (14.45 degrees F).
- 600 seconds have been passed since start-up.

(Condition 3)
- Ignition ON with the engine running.
- Start-up IAT is between 9.75 degrees C (49.55 degrees F) and 50.25 degrees C (122.5 degrees F).
- Ambient air temperature is higher than 9.75 degrees C (49.55 degrees F).
- Difference of start-up IAT and ambient temperature is less than 15 degrees C (59 degrees F).

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF at the end of 3 consecutive validation cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
Check for any of the following conditions:
- Check for the proper operation of the engine 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.
- Check for a faulty electrical connection to the ECM.

An intermittent malfunction may be caused by a fault in the ECT sensor electrical circuit. Inspect the wiring harness and components for an intermittent condition. Repair any electrical circuit faults that were found. 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.

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DTC Troubleshooting