What does P0109 mean?
The manifold absolute pressure (MAP) sensor measures pressure (vacuum or boost) inside the intake manifold. The computer uses it for fuel and ignition timing, and on turbo engines to monitor boost.
The signal is dropping out or jumping erratically for short periods.
Codes are a starting point. They tell you which test failed, not which part to replace. Check for other stored codes and fix those in a sensible order.
Symptoms
- Check engine light
- Rough idle
- Hesitation
- Poor fuel economy
- Hard starting
Common causes
- Loose connector or chafed wire that loses contact over bumps
- Corrosion in the connector
- Sensor failing intermittently
How to diagnose P0109
- Wiggle-test the harness while watching live data for dropouts.
- Check the connector terminals for spread pins and corrosion.
- Check the harness where it passes brackets, the engine and hot exhaust parts.
- With the key on and engine off, the MAP reading should match barometric pressure (about 14.7 psi / 101 kPa at sea level).
- At warm idle, a healthy gas engine usually shows roughly 18 to 22 inHg of vacuum (around 25-35 kPa).
How to fix it
- Replace the vacuum hose
- Repair wiring
- Replace the MAP sensor
Estimated repair cost
Likely repairs for P0109 run from about $100 to $450, depending on the cause.
| Repair | Typical range (parts + labor) |
|---|---|
| Diagnostic fee (scan + testing) | $100 - $200 |
| MAP sensor replacement | $100 - $300 |
| Vacuum leak repair (hose/gasket) | $100 - $450 |
These are rough US estimates for an independent shop in 2026, based on typical parts prices and standard labor times. Dealers, big trucks, luxury brands and high-cost areas often run higher. They are not quotes. Use the repair cost estimator to adjust for your vehicle.
How serious is P0109?
Moderate severity
Usually drivable, but fuel economy and performance will suffer.
P0109 FAQ
What does P0109 mean?
P0109 stands for "Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent". The manifold absolute pressure (MAP) sensor measures pressure (vacuum or boost) inside the intake manifold.
Can I drive with a P0109 code?
Usually drivable, but fuel economy and performance will suffer.
How much does it cost to fix P0109?
It depends on the cause. The likely repairs for P0109 range from about $100 to $450 at an independent shop in the US, plus a diagnostic fee of roughly $100-$200. These are rough estimates; dealer prices and some vehicles run higher.
What is the most common cause of P0109?
The most common causes are: loose connector or chafed wire that loses contact over bumps; corrosion in the connector; sensor failing intermittently.