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.
Code P1111, IAT Intermittent High - "S" & "T" Series 4.3L (VIN W): Notes
Intake Air Temperature (IAT) sensor is a thermistor. Control module applies and monitors 5 volts on circuit to sensor. When air is cold, sensor resistance is high and control module will measure a high signal voltage. If air is warm, sensor resistance is low causing control module to measure low voltage.
- Tech 1 may be used to diagnose this fault since control module transmits actual values when fault is present. A grounded circuit will cause Tech 1 to display a temperature of about 297°F (147°C).
- If Tech 1 displays -40° with IAT sensor disconnected, control module and wiring are okay. Replace IAT sensor.
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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.