P0116 Code – Engine Coolant Temperature Circuit Range/Performance Problem

Meaning:

P0116 triggers when the PCM has detected a sudden change in engine coolant temperature
When the PCM has seen a sudden and quick change in engine coolant temperature, P0116 happens

The PCM has seen a sudden and quick change in engine coolant temperature (ECT) at a time when there shouldn’t be such a change.

Main Symptoms:

  • Check Engine Light comes on
  • Poor fuel economy
  • Engine fails to idle and may not start completely
  • Engine produces black smoke (visible at tailpipe)

Possible Causes:

  • Thermostat is either missing or open
  • Defective ECT sensor
  • Open or short in ECT signal or ground circuit

Diagnostic Steps:

  • Using an OBD2 scanner, start by diagnosing and resetting any other ECT codes
  • Now, check the ECT reading. When the engine is cold the reading should match ambient temperature reading. If it doesn’t then there’s a problem with the ECT sensor

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