Code Definition

P1109 — Intake Air Temperature B circuit intermittent

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

About P1109

P1109 is a manufacturer-specific powertrain diagnostic trouble code recorded for Ford vehicles. 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 an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

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

The P1109 code indicates the PCM has detected an intermittent fault in the Intake Air Temperature (IAT) Sensor B circuit. IAT Sensor B is a second intake air temperature sensor, often located in the intake manifold or charge air path on turbocharged and some larger engines, and it is usually a thermistor whose resistance falls as air temperature rises. The PCM uses this reading to fine tune fuel delivery, ignition timing, and on boosted engines the charge cooling strategy. Because the fault is intermittent, the signal drops out or jumps only briefly, which can cause occasional driveability cha...

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