Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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 the 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.
- This step determines if DTC 48 is the result of a hard failure or an intermittent condition.
- This step determines if the IAT signal circuit is shorted to ground.
- This step determines if a wiring problem is present or if PCM is faulty.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.