Parts for your 2018 Subaru Forester-Map sensor

2018 Subaru Forester MAP sensor — what it does and when to service it

Yes, the 2018 Subaru Forester is fitted with a MAP (manifold absolute pressure) sensor. It’s an engine control input used on both the 2.5-litre FB25 (non‑turbo) and 2.0‑litre FA20DIT (turbo/XT) variants. This is documented in Subaru’s 2018MY Forester Service Manual (STIS), Engine (Diagnostics) sections listing “Manifold Absolute Pressure Sensor (MAP)” as an ECM input, and shown in the Subaru Electronic Parts Catalogue under the intake manifold/throttle body group as “Sensor – Manifold Absolute Pressure.” OBD‑II diagnostics used by Subaru also define MAP‑related DTCs (P0105–P0108) for this model.

On a 2018 Forester, the MAP sensor reads the absolute pressure inside the intake manifold so the ECU can calculate air mass, fuel delivery, and ignition timing. On turbo XT models, it also helps the ECU manage boost and knock control. It works alongside the MAF sensor, giving the ECU a second view of engine load for better drivability from sea level to the high country.

It generally lives on or near the top of the intake manifold with a small vacuum port and a plug for the 5‑volt reference, ground, and signal. When it goes out of whack, the Forester can feel doughy off the line, chew more petrol than usual, or throw a check‑engine light. Common codes include P0106 (range/performance), P0107 (low input), and P0108 (high input).

• Typical symptoms: rough idle, flat spots, poor fuel economy, hard starts, and MAP‑related DTCs.
• Basic checks: inspect the connector for corrosion, ensure the O‑ring seals properly, and confirm the port isn’t blocked by oil mist.

There’s no set replacement interval in Subaru’s schedule, the MAP sensor is replaced on condition. As part of routine servicing, it’s smart to visually inspect it every 20,000–30,000 km. If contamination is visible, a light clean with sensor‑safe electronics cleaner can help—no harsh solvents, no poking the port with wire. On turbo XT models, also make sure PCV and intercooler plumbing aren’t feeding excess oil vapour into the manifold.

Replacement is straightforward: disconnect the battery, unplug the connector, remove the retaining screw, swap the sensor and O‑ring, and refit. Always tighten to the service‑manual spec and clear any fault codes, then take a short drive so the ECU can relearn trims. If a fresh sensor doesn’t resolve MAP‑related faults, a smoke test for intake leaks and checks of the 5‑volt reference/ground integrity under the bonnet are the next steps a technician will take.

Technical references

• Subaru 2018MY Forester Service Manual (STIS): Engine (Diagnostics) – ECM Inputs: Manifold Absolute Pressure Sensor (MAP)
• Subaru Electronic Parts Catalogue (EPC): Intake manifold/throttle body group – Sensor, Manifold Absolute Pressure
• OBD‑II/SAE J1979 DTC set used by Subaru (P0105–P0108 for MAP circuit and performance)

Popular questions

Where is the MAP sensor on a 2018 Forester?
It’s mounted on the intake manifold, near the throttle body. On the 2.5‑litre it sits on top with a single fastener and a 3‑pin plug. Turbo XT models also have it on the manifold, separate from the charge‑pipe pressure sensor.

Can a MAP sensor be cleaned or does it need replacement?
If it’s just light oil mist, a careful clean with sensor‑safe electronics cleaner can restore readings. If the sensor is electrically faulty or repeatedly sets P0106/P0107/P0108 after checks, replacement is the go.

What are the signs of a failing MAP sensor?
Sluggish throttle response, rough idle, higher fuel use, and a check‑engine light are common. The ECU may log MAP codes and the car can feel like it’s lost its spark, especially under load or changing altitude.