Parts for your 2015 Subaru Impreza-Maf sensor

2015 Subaru Impreza MAF Sensor — What it does and how to look after it

Technical documentation confirms the 2015 Subaru Impreza (GJ/GP with the FB20 2.0‑litre engine) is fitted with a Mass Air Flow (MAF) sensor. The Subaru Service Manual (STIS) for the FB20 engine details the “MAF & IAT sensor” and related diagnostic trouble codes (P0100–P0104), and the OEM parts catalogue for MY2015 Impreza lists a mass air flow sensor assembly in the intake duct. These factory sources leave no doubt the MAF sensor is relevant and used on this model.

On this Impreza, the MAF sits in the intake snorkel just after the airbox and before the throttle body, measuring how much air the engine is breathing and the intake air temperature (the IAT is integrated). The engine control module uses that data to nail fuel trims, timing and emissions. Subaru also equips the FB20 with a manifold absolute pressure (MAP) sensor, but the MAF is the primary airflow input during normal running.

As part of regular servicing, the MAF sensor deserves a quick check because a dirty or failing unit can cause rough idle, flat spots, higher fuel use, and a glowing MIL. It’s common in Australia and New Zealand for dust, oil vapour, or over‑oiled aftermarket filters to leave a film on the sensing element.

• Typical signs of a crook MAF: hesitant acceleration, poor economy, surging, and codes like P0101–P0104.
• Common causes: intake leaks after the airbox, contaminated element, or wiring/connector issues.

1. Inspection and cleaning: With the engine cool, unplug the connector, remove the two fasteners, and lift the sensor straight out. Only use a dedicated MAF cleaner—never touch the element with fingers or cloth. Let it air dry fully before refitting with the O‑ring seated properly.
2. Service rhythm: There’s no fixed replacement interval from Subaru, but a preventative clean every 40,000–60,000 km (or sooner in dusty conditions) keeps readings crisp.
3. Replacement: If cleaning doesn’t stabilise trims or the scan tool shows out‑of‑range airflow at idle/part‑throttle, replace with a quality OEM‑spec unit. Avoid over‑tightening the screws and make sure the connector locks home.
4. Post‑service drive: The ECU will relearn trims after a short mixed drive. No special procedures are usually required.

A healthy MAF helps the 2015 Impreza run smoothly, sip less petrol, and pass emissions without fuss. Keeping the intake airtight and the sensor clean is simple, low‑cost insurance for long engine life.

• Where is the MAF sensor on a 2015 Subaru Impreza?
  The MAF is mounted in the intake duct just after the air filter box on the driver’s side, secured with two screws and a multi‑pin plug. Pop the airbox lid and follow the snorkel towards the throttle body—it’s right there in plain sight under the bonnet.
• Should it be cleaned or replaced?
  Light contamination is often sorted with proper MAF cleaner. If symptoms persist, trims won’t settle, or DTCs return, fit an OEM‑spec replacement. Always check for intake leaks and the condition of the air filter first.
• Can it run with the MAF unplugged?
  It may start and default to speed‑density using the MAP sensor, but it’ll run poorly and log a fault. That’s a roadside diagnostic trick at best—not a way to drive. Reconnect and repair for normal operation.