Parts for your 2021 Subaru Impreza-Map sensor

2021 Subaru Impreza MAP sensor — what it does and how to look after it

According to Subaru’s factory service manual for the 2017–2021 Impreza (FB20D engine, GK/GT chassis) — see the Engine Diagnostics sections for DTCs P0106–P0108 — and the Subaru FAST parts catalogue listings for “Sensor, Manifold Absolute Pressure,” the 2021 Subaru Impreza is fitted with a MAP sensor mounted on the intake manifold. OE supplier data (Hitachi/NTK listings for FB20) also confirms fitment. So yes, the MAP sensor is absolutely relevant on this model.

The MAP sensor measures the absolute pressure inside the intake manifold. The engine control module (ECM) uses that signal to understand engine load, fine-tune fuel and ignition, and keep things smooth across Aussie and Kiwi conditions — from sea level commutes to alpine passes. On the FB20D, the ECM uses both the MAF and MAP signals, the MAP provides quick-response load data, altitude compensation, and cross-checks for diagnostics.

Signs the Impreza’s MAP sensor needs attention include a check engine light, rough idle, poor fuel economy, black exhaust smoke, hard starting, or hesitant throttle. Common codes are P0106 (range/performance), P0107 (low input), and P0108 (high input). With ignition on/engine off, scan data should read near local barometric pressure (~100 kPa at sea level). At hot idle on a healthy naturally aspirated FB20, expect roughly 30–45 kPa, opening the throttle should sweep smoothly towards ambient.

There’s no fixed replacement interval — it’s a monitor-and-maintain item. During routine servicing:

• Visually check the connector and harness under the bonnet for rub-through or corrosion.
• Confirm the sensor’s O-ring is intact and the port isn’t blocked by carbon or oil mist.
• If contaminated, remove and clean gently with electronics-safe MAF/MAP cleaner. Don’t poke the sensing element or use compressed air.
• Refit carefully, don’t overtighten. Clear any fault codes and verify readings on a scan tool.

If faults persist after cleaning and wiring checks, replacement is straightforward and typically involves a single fastener and a plug. Use quality OE-spec parts to avoid drift or slow response. After replacement, a short drive cycle will let the ECM relearn, you can also reset learned values with a scan tool. Kept clean and connected properly, the MAP sensor helps the Impreza run crisply, sip less fuel, and pass emissions without dramas.

Popular questions about the 2021 Subaru Impreza MAP sensor

Does the 2021 Impreza have both a MAF and a MAP sensor?
Yes. The FB20D engine uses a MAF sensor in the intake duct and a MAP sensor on the manifold. Subaru’s service manual wiring diagrams and diagnostics confirm both inputs are used for load calculation and self-diagnostics.

How often should the MAP sensor be replaced?
It isn’t a scheduled replacement item. Inspect at each service, clean only if dirty, and replace if readings are out of spec, faults return after cleaning, or DTCs P0106–P0108 persist alongside verified power/ground integrity.

Where is the MAP sensor located on the 2021 Impreza?
It’s mounted on the intake manifold with a small O-ring seal and a three-pin connector. Access is under the bonnet, removal is usually a single bolt and a connector release.