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.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- MAP connector loose or corrodedCommon
- Sensor fails when hotPossible
- Wiring chafed or pinchedPossible
Parts involved
- MAP Sensor
- MAP Connector
- MAP Wiring
P0109 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.