Parts for your 2009 Subaru Legacy-Map sensor

2009 Subaru Legacy MAP sensor — what it does and how to look after it

Yes, the 2009 Subaru Legacy is fitted with a MAP (manifold absolute pressure) sensor. This applies to both the naturally aspirated 2.5i (EJ253) and the turbocharged 2.5GT (EJ255). This is documented in the Subaru Factory Service Manual for 2009 Legacy/Outback (Engine Diagnostics sections for H4SO and H4DOTC, covering DTCs P0106–P0108/boost pressure sensing) and is reflected in the Subaru FAST electronic parts catalogue, which lists the manifold pressure/boost sensor for these models.

On this model, the MAP sensor helps the engine control unit work out engine load by reading pressure inside the intake manifold. It’s teamed with the MAF sensor on many variants, letting the ECU cross-check airflow and pressure for clean drivability, good fuel economy, and proper ignition timing. On turbo cars it also keeps tabs on boost so the ECU can control wastegate duty and protect the engine.

Location-wise, owners will find the MAP sensor mounted on or near the top of the intake manifold. On naturally aspirated cars it’s typically right by the throttle body, sealed with an O-ring. Turbo models place it on the manifold where it can see vacuum at idle and positive pressure on boost.

There’s no scheduled replacement interval, but it’s smart to inspect the MAP sensor during major services (or any time a check engine light pops up). With the key on, engine off, scan data should read close to local barometric pressure (around 100 kPa at sea level). At hot idle, a healthy NA engine usually shows roughly 30–45 kPa, a turbo car will show vacuum at idle and positive kPa under load. If readings look odd, check power, ground and signal, and make sure the O-ring seats properly.

• Common symptoms of a dodgy MAP: rough idle, flat spots on acceleration, poor fuel economy, hard starting, black smoke, or DTCs such as P0106, P0107 and P0108.
• Quick care tips: avoid blasting solvent into the port, if there’s oily residue, a gentle wipe and a light sensor-safe cleaner mist on the tip is fine. Don’t poke the sensing hole.
• Replacement is simple: disconnect the plug, remove the retaining screw(s), lift out the sensor, lightly oil the new O-ring, refit and snug the screw(s). Clear codes and verify live data.

Use a quality OEM-equivalent sensor and resist overtightening—just firm with a small spanner or driver is plenty. On turbo models, be sure any boost leaks, split hoses or intercooler issues are sorted before blaming the MAP. After replacement, the ECU usually needs no special relearn, a short drive cycle will settle trims nicely.

Popular questions about the 2009 Subaru Legacy MAP sensor

Does the 2009 Legacy run both a MAF and a MAP sensor?
Yes, many 2009 Legacy variants use both. The MAF sits in the intake snorkel/airbox measuring incoming airflow, while the MAP reads pressure inside the manifold. The ECU blends these signals for accurate load calculation, altitude compensation and smooth throttle response.

Where exactly is the MAP sensor on a 2009 Legacy?
It’s typically on the top of the intake manifold near the throttle body on non‑turbo cars. On turbo models it’s mounted on the manifold where it can see both vacuum at idle and boost under load. Look for a small rectangular sensor with a single electrical connector and a sealing O‑ring.

What fault codes point to a MAP sensor issue?
Common MAP‑related codes include P0106 (range/performance), P0107 (low input) and P0108 (high input). On turbo cars, abnormal boost codes can also show up if the MAP/boost reading is off. Always verify power/ground, connector condition and manifold leaks before replacing the sensor.