Code 23, Intake Air Temp Sensor CKT/Low Temp Indicated

IAT sensor uses a thermistor to control signal voltage to ECM. ECM applies 4-6 volts on Red/Black wire to the sensor. When intake air is cold, sensor resistance is high. ECM will sense high signal voltage. As intake air temperature warms, sensor resistance decreases, and voltage drops.

1. Code 23 is set if signal voltage indicates intake air temperature is less than -31°F (-35°C) for 5 seconds.
2. If resistance is less than 100 ohms, replace IAT sensor.

Fig 1: Code 23 Flow Chart, IAT Sensor Ckt./Low Temp. Indicated

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 23 Schematic, IAT Sensor Ckt./Low Temp. Indicated

Courtesy of GENERAL MOTORS CORP.