P0109
Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent
Fuel & air metering
Generic OBD-II
High
What it means
P0109 means the computer detected an intermittent, dropping-out signal from the MAP (manifold absolute pressure) sensor, which measures intake pressure to help set fueling. Because the reading comes and goes, the fault is most often a loose connector or chafed wire, and it can cause hesitation or stalling when the signal glitches.
High
Can I keep driving? You can usually drive, but an intermittent MAP signal can cause sudden hesitation or stalling, so treat it as urgent if the engine surges or cuts out.
Common symptoms
What you'll notice
- Check-engine light on
- Hesitation, surging, or occasional stalling
- Poor fuel economy
- Lack of power on acceleration
Common causes
Most likely first
- Loose or corroded connector at the MAP sensor (most common for an intermittent fault)Likely
- Chafed or intermittently broken wiring in the sensor circuitCommon
- Failing MAP/barometric pressure sensor with a dropping-out signalCommon
- Vacuum leak or damaged vacuum line to the sensorLess often
- Rarely, an ECM/PCM faultLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data to see the conditions when the signal drops out.
- Inspect the MAP sensor connector and pins for corrosion, spread terminals, or looseness.
- Wiggle-test the harness and connector with the engine running to reproduce the fault.
- Check the sensor's vacuum source (if applicable) and the signal, ground, and reference wires.
- Replace the MAP sensor if the wiring and connector are good. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0109?+
Short trips are usually fine, but because the MAP signal helps set fueling, an intermittent dropout can cause stalling or hard hesitation. Fix it promptly if the engine cuts out or surges.
Can I just clear P0109?+
It will return whenever the signal glitches again. Since this is an intermittent code, concentrate on the connector and wiring before replacing the sensor.
Related codes
Often seen with P0109
Read & clear P0109 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX