Code 23, Intake Air Temp CKT/High Temp Indicated

The IAT sensor uses a thermistor to control signal voltage to ECM. ECM applies 4-6 volts on Blue/Black wire to sensor. When intake manifold air is cold, the sensor (thermistor) resistance is high, and ECM senses high voltage. As intake air warms, sensor resistance decreases, and the voltage drops.

1. This checks if Code 23 is due to a hard failure or an intermittent condition. Code 23 is set if IAT temperature is greater than 293°F (145°C) for more than 2 seconds.