Parts for your 2015 Subaru Impreza-Oxygen sensor

2015 Subaru Impreza oxygen-sensor: purpose, upkeep, and when to replace

Technical sources confirm the 2015 Subaru Impreza is fitted with oxygen-sensors. The Subaru factory service information for the FB-series 2.0L engine specifies a front air–fuel ratio (A/F) sensor upstream of the catalytic converter and a rear oxygen sensor downstream. Subaru diagnostic documents list related DTCs (e.g., P0131, P0132, P0134, P0137, P0138, P0141 and P0420), and mainstream service manuals and parts catalogues for the 2015 Impreza show two sensors in the exhaust system. These align with OBD‑II requirements for closed‑loop fuel control and catalyst monitoring used on petrol engines of this era.

The 2015 Subaru Impreza relies on two oxygen-sensors to keep fuelling spot on and emissions low. The front A/F sensor (often called the wideband O2) continuously measures the oxygen content in exhaust so the ECU can fine‑tune the air–fuel ratio, helping the car run smoothly, use less fuel, and protect the catalytic converter. The rear oxygen-sensor sits after the cat and mainly checks how well the converter is cleaning up the exhaust. If those readings aren’t right, you’ll usually see a check engine light and codes like P0420.

As part of regular servicing, there’s no scheduled replacement interval in the owner’s book, but many techs see sensors getting sluggish somewhere around 150,000–200,000 km, depending on driving and fuel quality. If fuel economy drops, idle gets a bit lumpy, the exhaust smells rich, or the dash light comes on with O2‑related codes, it’s time for testing and likely replacement.

Good practice during service is to inspect the sensor wiring and connectors for heat damage or fraying, check for exhaust leaks (especially ahead of the front sensor), and avoid silicone sprays or sealants that can poison a sensor. If a sensor needs replacing, use a quality OEM‑equivalent wideband for the front and the correct downstream sensor for the rear. A proper O2‑sensor socket helps prevent damage, and a hint of anti‑seize on the threads is typically pre‑applied by reputable brands—so don’t add more unless the manufacturer says so. After fitting, clear codes and let the ECU relearn trims with a decent drive cycle. If the light returns, rule out vacuum leaks, misfires, or a tired catalytic converter before throwing more parts at it.

Look after the oxygen-sensors and the Impreza rewards with cleaner running, better fuel economy, and less hassle at WOF or rego time.

• How many oxygen-sensors does a 2015 Subaru Impreza have?
• When should the oxygen-sensors be replaced?
• Is it safe to drive with a faulty oxygen-sensor?

How many oxygen-sensors does a 2015 Subaru Impreza have?
The 2015 Impreza has two: a front wideband air–fuel ratio sensor before the catalytic converter and a rear oxygen-sensor after it. The front controls fuelling, the rear monitors catalyst efficiency.

When should the oxygen-sensors be replaced?
There’s no fixed interval, but many fail or slow down around 150,000–200,000 km. Replace sooner if there’s a check engine light with O2‑related codes, poor economy, rough running, or after confirmed testing shows a lazy sensor.

Is it safe to drive with a faulty oxygen-sensor?
Short term, the car will usually run, but it may use more fuel, pollute more, and risk catalyst damage. Prolonged driving with a bad sensor can get expensive—sort it promptly.