P0109Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The manifold absolute pressure (MAP) sensor measures the pressure behind the throttle; on vehicles without a separate barometric sensor it also supplies the ambient pressure, read at key-on or wide-open throttle – hence 'MAP/BARO'. It is a three-wire sensor with 5 V reference, ground and signal. P0109 counts brief range violations of the signal that are too short for P0107/P0108 – the typical signature of a loose contact. Ford counts excursions below 0.024 V or above 4.96 V and sets the code after 25 events per drive cycle (2020–2023; ten in 2012). Ford treated it as a code without warning light in 2012 but lights the MIL in 2020–2023, so the warning-light behaviour depends on the manufacturer. GM does not use P0109 in the tables checked; there short dropouts accumulate in P0107/P0108.
- What you may notice
- Check engine light on (depending on manufacturer)
- Occasional hesitation or stumble
- Fault comes and goes
- Likely causes
- LikelyLoose contact at the MAP connector, terminals spread or corroded
- PossibleChafed or broken wire that makes contact with engine movement
- PossibleSensor with internal dropouts
- RareGround problem or control module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €20 – €200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.