Code Definition

P1111 — IAT Sensor Circuit Intermittent Voltage High

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

About P1111

P1111 is a manufacturer-specific powertrain diagnostic trouble code recorded for Isuzu 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

This Isuzu code indicates the Intake Air Temperature (IAT) sensor is intermittently reporting a voltage higher than the expected range. The IAT sensor is a thermistor whose resistance falls as intake air warms, and the Engine Control Module (ECM) reads the resulting voltage to correct fuel injection and ignition timing for air density. Because the sensor signal rises with resistance, an intermittent high voltage typically reflects a brief open or high resistance in the circuit, which the ECM sees as an implausibly cold air temperature. The sporadic fault can cause hesitation, hard starting, or...

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