74 ECT/Trans Temp Sensor Ratio Error

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The coolant temperature sensor (CTS) is a thermistor located in a coolant passage on the engine. When coolant temperature is cold the sensor has a high resistance, as temperature increase the resistance of the sensor decreases. The PCM provides a five volt signal to the coolant sensor, which is also connected to PCM ground. The PCM reads the voltage drop on the signal line to determine coolant temperature.

Information Flag Parameters

Information Flag 74 will set if:

  • The transmission temperature sensor is functioning properly.
  • The CTS reading is less than Transaxle Temperature Sensor (TTS) reading

Diagnostic Aids

  • Information Flag 74 is used to indicate a degrading CIS. Remove the CTS and inspect for contamination.
  • Measure resistance through the CTS by attaching female terminals to the two CTS pins.
  • The resistance reading should be 2786 ohms 40 ohms at room temperature (25°C [77°F]).

NOTICE: Information flags should be used for diagnostic purposes only. They do not necessarily indicate component malfunction/failure.