DTC 48, IAT Sensor Circuit High (Low Temperature Indicated): Notes

Intake Air Temperature (IAT) sensor is a thermistor that controls signal voltage to PCM. When air is cold, sensor resistance is high, and PCM will sense a high signal voltage. As air warms, sensor resistance becomes less and voltage drops. DTC 48 will set when intake air temperature is less than -39°F (-38°C) for 2 minutes. PCM will default to poor engine performance during cold operation.

1. This step determines if DTC 48 is result of a hard failure or an intermittent condition.
2. This step determines if IAT signal circuit is shorted to ground.
3. This step determines if a wiring problem is present or if PCM is faulty.