P0109 code meaning
Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent
Powertrain system Generic code P01xx codes Check engine light
What P0109 means
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.
P0109 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0109
- Check engine light on (depending on manufacturer)
- Occasional hesitation or stumble
- Fault comes and goes
Common causes of P0109
- Most likelyLoose contact at the MAP connector, terminals spread or corroded
- PossibleChafed or broken wire that makes contact with engine movement
- PossibleSensor with internal dropouts
- Less likelyGround problem or control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Manifold absolute pressure sensorSensor wiringSensor reference voltage
What each part of P0109 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 09 | The exact fault in that area. |
What to do next
- Note P0109 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0109
What does P0109 mean?
P0109 means "Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent". 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 generic code, so it means the same on every make.
Is it safe to drive with P0109?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0109 fail an emissions test?
Yes, it can. P0109 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0109 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0109 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.