For 1990-2009 cars

The engine coolant temperature (ECT) sensor is a thermistor that varies resistance according to changes in engine coolant temperature. When the sensor is cold it has a high resistance (high signal voltage at PCM). During a cold start the ECT and intake air temperature (IAT) readings are compared. DTC P0116 sets after the powertrain control module (PCM) verifies proper operation of the IAT sensor and the difference between ECT and IAT reading does not fall within an acceptable range.

### DTC Parameters

DTC P0116 will set if the difference between startup ECT and IAT is greater than 15°C (44°F) when:

• | The engine has been turned OFF for longer than 7 hours and 30 minutes.

• | The startup IAT is greater than 10°C (50°F)

• | The vehicle has traveled greater than 16 km/h (10 mph) for longer than 10 seconds

• | the IAT has increased by at least 3°C (5.4°F) since startup.

• | No IAT or ECT DTCs have been set.

DTC P0116 runs once per ignition cycle once the above conditions have been met.

DTC P0116 is a type B DTC.

### Diagnostic Aids

DTC P0116 indicates a skewed ECT sensor reading that most likely was not caused by a wiring fault.

Engine coolant leaking from the sensor into the sensor connector will cause a shorted condition across the sensor terminals resulting in an elevated temperature.

Use of an engine block heater at temperatures greater than 0°C (32°F) may cause DTC P0116 to set.

Refer to Engine Controls Component Descriptions for a Temperature versus Resistance chart.