P0109 — Manifold Absolute Pressure / Barometric Pressure Circuit Intermittent
The ECU detects intermittent signal dropouts on the MAP/BARO sensor circuit. Fault is not constantly present — typically caused by loose connectors, chafed wiring, or a sensor failing under thermal load.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Map sensor
- Map connector
- Map wiring
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- MAP connector loose or corroded
- Sensor fails when hot
- Wiring chafed or pinched
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.