P0175 on a Subaru: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

Drivable short-term, but a rich mixture wastes fuel and can foul spark plugs or overwork the catalytic converter if ignored.

What P0175 means on a Subaru

On a Subaru, P0175 means the engine is running rich on bank 2. Only Subaru's six-cylinder boxer engines, like the 3.6L in the Outback and Tribeca, have two banks. The computer has reduced fuel as far as it can and still sees too much fuel or too little air.

Is P0175 common on Subarus?

P0175 is tied to Subaru's H6 models, most commonly the Outback 3.6R and the Tribeca. Subaru mass air flow sensors are sensitive and are a frequent cause of rich running when they get dirty or fail. Leaking fuel injectors and slow oxygen sensors are also common on higher-mileage H6 engines.

Commonly reported on: Outback, Tribeca, Legacy.

Symptoms

Check engine light is on
Poor fuel economy
Fuel smell from the exhaust
Rough idle or hesitation

Common causes

most common: Dirty or failing mass air flow (MAF) sensor
common: Leaking fuel injector on bank 2
common: Slow or failing oxygen sensor on bank 2
less common: Fuel pressure too high
less common: Restricted exhaust from a clogged catalytic converter

How to fix it

Fix	DIY?	Typical cost
Clean the MAF sensor with MAF cleaner spray	Yes	$10–20
Replace the leaking injector on bank 2	Mechanic	$250–600
Replace the bank 2 upstream oxygen sensor	Yes	$80–250
Have the fuel system and exhaust checked	Mechanic	$100–300

Frequently asked questions

Do all Subarus have a bank 2?

No. Bank 2 exists only on six-cylinder Subarus like the Outback 3.6R and the Tribeca. Four-cylinder boxer engines set P0172 instead.

Why is the MAF sensor a common cause on Subarus?

Subaru MAF sensors are sensitive to dirt and oil. When they read low, the computer adds extra fuel and the engine runs rich. Cleaning it is a cheap first step.

Is it safe to drive my Subaru with P0175?

For short trips, yes. A rich mixture can foul plugs and overwork the catalytic converter, so have it diagnosed soon.