Code Definition

P1109 — IAT - B Sensor Intermittent

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

About P1109

P1109 is a manufacturer-specific powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1109 is stored, the module has detected 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.

P1109 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 code is set when the powertrain control module (PCM) detects an intermittent signal from the Intake Air Temperature (IAT) Sensor B. The IAT sensor measures the temperature of incoming air and provides a voltage signal to the PCM, which adjusts fuel delivery and ignition timing accordingly. An intermittent signal suggests a wiring issue, sensor fault, or poor electrical connection.

Quick Facts