Parts for your 2014 Subaru Forester-Oxygen sensor

2014 Subaru Forester Oxygen Sensor (O2/A‑F) — Purpose, servicing and when to replace

Yes, the 2014 Subaru Forester uses oxygen sensors. Technical sources confirm this: the Subaru Forester SJ 2014 Factory Service Manual (Engine Control/Fuel Injection sections) specifies an upstream Air‑Fuel Ratio (A/F) sensor and a downstream Heated Oxygen Sensor for petrol engines (FB20/FB25 and FA20DIT). Subaru diagnostic charts list related DTCs (e.g., P0131–P0161, P0420), and Australian/New Zealand emissions compliance under ADR 79 (Euro 5 era) requires closed‑loop lambda control. So the oxygen sensor is absolutely relevant on this model.

On the 2014 Forester, the front wideband A/F sensor sits before the catalytic converter and constantly feeds data so the ECU can fine‑tune fuel trims. The rear O2 sensor sits after the cat and monitors catalytic converter efficiency. Together they help the Forester run smoothly, keep fuel economy in check, and meet emissions standards.

While these sensors aren’t a routine “every-service” replacement item, their performance can degrade over time. Many see 150,000–200,000 km, but fuel quality, short‑trip driving, and exhaust leaks can shorten that. If the check engine light pops up with codes like P013A, P0134 or P0420, if there’s a whiff of fuel, rough idle, or increased fuel use, it’s time to test or replace.

• Inspection tips: Check for exhaust leaks ahead of the sensors, damaged wiring or brittle connectors, and soot or contamination on the sensor body.
• Replacement pointers: Let the exhaust cool, use a proper O2 sensor socket, support the harness so it doesn’t twist, and seat the new sensor to the workshop‑manual torque spec. Most genuine sensors come pre‑coated on threads—avoid extra anti‑seize unless specified.
• After fitment: Clear codes, perform an ECU relearn/drive cycle, and verify fuel trims and readiness monitors.

Choosing parts: A genuine Subaru A/F sensor and rear O2 sensor will match the ECU’s calibration. Quality OEM‑equivalent units can also work well, steer clear of poorly crimped “universal” leads that can cause intermittent faults.

As part of regular servicing on a 2014 Forester, it’s smart to scan for pending codes, review short‑ and long‑term fuel trims, and visually inspect the sensors and exhaust. That bit of attention helps keep the boxer engine running sweet and saves fuel over the long haul.

Popular questions

How many oxygen sensors does a 2014 Subaru Forester have?
Most petrol 2014 Foresters run two: one front A/F sensor (upstream) and one rear O2 sensor (downstream). Turbo XT models also use the same upstream/downstream arrangement. Exact fitment can vary by market and engine code, but two is the norm.

What are the signs the O2 sensor needs replacing?
Look for a check engine light with codes like P0134, P013A or P0420, rough idle, higher fuel consumption, or a fuel smell. A lazy front A/F sensor often shows trims drifting rich or lean, a failing rear sensor might trigger catalyst efficiency faults.

Can it be driven with a faulty oxygen sensor?
Usually yes for a short period, but the ECU may default to richer mixtures, wasting fuel and risking catalyst damage. It’s best to diagnose and sort it promptly to avoid bigger repair bills.