Code Definition

P1111 — Intake Air Temperature Sensor Circuit Intermittent High Voltage

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: GM

About P1111

P1111 is a manufacturer-specific powertrain diagnostic trouble code recorded for GM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1111 is stored, the module has detected a signal or supply voltage higher than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1111 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The Intake Air Temperature (IAT) sensor is a negative temperature coefficient thermistor whose resistance falls as intake air warms, and the Powertrain Control Module (PCM) reads the resulting voltage to measure incoming air temperature for fuel and timing calculations. The PCM applies a reference voltage through an internal resistor, so when the sensor is cold the signal voltage is high and when the air is hot the voltage is low. DTC P1111 sets when the PCM sees the IAT signal voltage spike intermittently to a high level, which corresponds to a momentary open or high resistance in the sensor ...

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