Code 23, Intake Air Temp Sensor Circuit Low Temp Indicated

IAT sensor uses a thermistor to control signal voltage to ECM. ECM applies 4-6 volts on Gray wire to sensor. When manifold air is cold, sensor resistance is high. ECM will sense high signal voltage. As air temperature warms, sensor resistance will be less, and voltage will drop.

1. Code 23 is set if signal voltage indicates manifold air temperature is less than -54°F (-48°C) for 2.7 seconds. This code is also set if an open exists in sensor or wire. This step determines if ECM and wiring are okay.
2. Check temperature and resistance values of IAT sensor against values in DIAGNOSTIC AID table. If resistance is out of specification, replace IAT sensor.