Trouble CodesGM OBD Trouble CodesGM Code 23

CODE 23 - Manifold Air Temperature Sensor

Trouble Code 23 indicates that the Manifold Air Temperature (MAT) sensor also known as the (IAT) Intake Air Temperature is reporting abnormally low readings. When the air is cold, the thermistor in the sensor has a high resistance, which falls as the air charge warms. Low readings thus indicate a possible bad sensor or open in the MAT circuit.

The conditions for setting this code are:

  • MAT/IAT reading is < -40 deg F (-40 deg C)

NOTE: A default MAT/IAT value indicating 82 deg F is used while Code 23 is present.

Typical thermistor resistance values are:

CTS Resistance Chart

Typical causes for this code include:

1) Defective MAT/IAT sensor
2) Open sensor ground circuit
3) Dirty or corroded connection(s) at MAT/IAT and/or ECM
4) Open circuit between the ECM and the MAT/IAT sensor
5) Defective ECM

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Chevy Trouble Codes