2015–2021 Subaru WRX

2015-2021 Subaru WRX — Engine Air Filter Replacement

By Ray Delgado ✓ Certified Mechanic · Published Sep 21, 2026 · Updated Oct 22, 2026

🔧 Easy 10-15 minutes $35 DIY

Save $75 by doing it yourself! Shop cost: $110

Quick answer: Engine Air Filter Replacement on a 2015–2021 Subaru WRX is rated Easy and takes about 10-15 minutes. You'll need 1 tool for this job, and parts cost about $35. This guide walks you through the full job step by step, including the mistakes to avoid.

Quick Video Tutorial

Parts You Need

Total Cost

$35.00

Part Name	Part Number	Price	Buy
Engine air filter for 2015-2021 Subaru WRX; verify engine, housing shape, and VIN fitment	—	$35.00	Amazon

About prices: shown prices are typical retail averages and change frequently; cheaper alternatives may be available. Confirm the current price before buying.

💡 Pro tip: Order all parts at once to save on shipping

Step-by-Step Instructions

Follow these steps carefully

Locate the airbox

Park on level ground, switch the engine off, and open the hood. No tools are strictly needed; a screwdriver helps with the intake clamp.

Unplug the MAF and release the fasteners

Press the release tab on the MAF sensor's electrical connector and unplug it — do this before moving anything, because the wiring has limited slack.

Lift the lid and pull the old filter

Set the lid aside carefully with the MAF sensor still attached to its tube. Lift the old rectangular panel filter out of the lower box and note the airflow arrow direction for reference.

Clean the housing — hands off the MAF

Vacuum or wipe the dust and leaf debris out of the lower box half, paying attention to the corners where the filter's rubber seal lands. Resist the urge to touch or spray anything on the MAF sensor element visible inside the intake tube — the sensing wires are delicate, and contamination throws off fueling. If the sensor looks visibly dirty, use a dedicated MAF cleaner spray only, never a rag.

🔧 Mechanic's note — Tom Becker

I know small thing, big difference: If the sensor looks visibly dirty, use a dedicated MAF cleaner spray only, never a rag.

Seat the new filter

Set the new filter into the lower box exactly as the old one sat, rubber sealing edge all the way around and any airflow arrow pointing the same way. Press down around the perimeter with your fingertips to confirm the seal sits flat against the box ledge — the FA20DIT's turbo will happily suck dirt past a pinched corner.

Close the lid and clamp it

Hook the lid's rear tabs into their slots at an angle, then lower the front down flush. Snap both metal spring clips back into place until they lock with an audible click.

🔧 Mechanic's note — Ray Delgado

I make it a point to do yourself a favor here: Snap both metal spring clips back into place until they lock with an audible click.

Start up and verify

Close the hood and start the engine. A forgotten MAF connector or a leaking lid seal shows up almost immediately as a rough idle or a CEL.

All Done!

Test your repair before closing everything up. If something doesn't work right, double-check your steps.

⚠️ Common Mistakes to Avoid

• Forgetting to reconnect the MAF sensor's electrical connector — the WRX will immediately run poorly and throw a code.
• Touching or trying to clean the tiny sensor wires inside the MAF housing with the lid off; they are fragile and even a fingertip can damage or contaminate them.
• Closing the lid without hooking the rear tabs in first — the clips will feel tight but the seal will leak and whistle.

Tools You'll Need

Flathead or Phillips screwdriver (intake clamp) Clean rag or shop vacuum MAF cleaner spray (optional, only if sensor is visibly fouled)

Related Trouble Codes

P0171 System Too Lean (Bank 1) P0101 Mass Airflow Sensor Range/Performance P0174 System Too Lean (Bank 2)

⚠️ Safety First!

• Let the engine cool before starting — the turbo sits right beside the airbox on the FA20DIT and stays hot long after shutdown.
• Never run the engine with the airbox open and no filter in place; the turbo can ingest debris in seconds.