DTC P1111 - IAT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE Pontiac Firebird IV

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

Circuit Description

Intake Air Temperature (IAT) sensor is a thermistor. PCM applies and reads a 5-volt reference signal to sensor. When air is cold, sensor resistance is high and PCM will measure a high signal voltage. If air is warm, sensor resistance is low causing PCM to measure low voltage.

Conditions required to set DTC are

1. No ECT, MAF or VSS sensor DTCs set.
2. Engine running longer than 3 minutes.
3. ECT greater than 140°F (60°C).
4. Vehicle speed less than 35 MPH.
5. IAT intermittently less than -38°F (-39°C).