25 IAT Circuit - Temperature Out of Range High

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The air temperature sensor (ATS) is a thermistor located in the air intake passage of the air induction system on the engine. When the sensor is cold it has a high resistance, the resistance decreases as the temperature of the sensor increases. The PCM supplies a five volt signal to the sensor which is also connected to ground. The PCM reads the voltage drop on the sensor signal line to determine air temperature.

Code Parameters

Code 25 will set if:

  • The ATS reading is over 125°C (257°F).

Diagnostic Aids

  • Refer to Temperature vs. Resistance chart.
  • When attempting to diagnose an intermittent problem, use the Scan Tool to review supplemental diagnostic information.
    • The supplemental data can be used to duplicate a problem. Select MALF History from Scan Tool EC menu.
  • Check the tightness of the female terminal grip with a spare male terminal.
  • ATS temperature may be compared to CTS temperature with a Scan tool if engine has cooled overnight at ambient temperature. They should be within four degrees of each other with ignition On and engine Off