Parts for your 2013 Subaru Impreza-Oxygen sensor

2013 Subaru Impreza oxygen sensor: purpose, servicing and when to replace

Based on the Subaru Factory Service Manual for the 2012–2016 Impreza (GJ/GP with the FB20 engine) and the Subaru diagnostic listings for OBD‑II faults, the 2013 Subaru Impreza is fitted with two exhaust gas sensors: a front Air/Fuel Ratio (A/F) sensor upstream of the catalytic converter (Bank 1 Sensor 1) and a rear oxygen sensor downstream of the converter (Bank 1 Sensor 2). These components are documented in the FSM’s Engine (Fuel Injection/Emission Control) and Diagnostics sections with DTCs such as P0131, P0134, P0137 and P0141, and are shown in Subaru’s OEM parts catalogues for this model year. So yes—oxygen sensors are absolutely relevant and used on this vehicle.

The front A/F sensor is a wide‑range sensor that lets the engine control unit fine‑tune the mixture during closed‑loop operation, keeping the burn right on target for smooth running, good petrol economy and low emissions. The rear oxygen sensor monitors catalytic converter efficiency. If the converter or front control goes off, the rear sensor’s readings flag it, helping the car meet ADR/OBD‑II compliance.

While there’s no fixed replacement interval in the factory schedule, these sensors are high‑heat, high‑duty items and can drift with age. Many owners see best results inspecting or testing around 100,000–160,000 kilometres, or sooner if fuel use climbs, the check engine light appears, or the car smells rich. The FSM supports diagnosis via live data and fuel trims, a scan tool reading odd short‑term/long‑term trims or lazy sensor response is a strong clue.

Good practice when servicing:

• Always let the exhaust cool fully, sensors live in the hottest bits under the bonnet.
• Use OEM‑quality parts (the Impreza’s A/F sensor is a heated wideband type, the rear is a heated narrowband). Universal cut‑and‑crimp units often cause dramas.
• Don’t contaminate the sensing tip—no grease or sealant. Many sensors arrive with the correct anti‑seize pre‑applied on the threads.
• Tighten to the factory torque (typically around 40–45 N·m for Subaru sensors—confirm in the FSM for the exact engine code).
• After replacement, clear codes and complete a proper drive cycle so the ECU relearns and the catalyst monitor sets.

Common signs an Impreza oxygen sensor is on the way out include rough cold starts, hesitation under light throttle, higher fuel burn, sulphur/sooty exhaust smell, and a glowing MIL with codes like P0134 (no activity) or P0141 (heater circuit). Leaving it too long can cook the catalytic converter, so it’s cheaper to sort the sensor early.

Popular questions

How many oxygen sensors does a 2013 Subaru Impreza have?
It runs two: a front Air/Fuel Ratio sensor before the catalytic converter and a rear oxygen sensor after the converter. The front handles mixture control, the rear checks the converter’s effectiveness. Both are heated and monitored by the ECU with OBD‑II diagnostics.

What are the typical trouble codes for these sensors?
Owners most often see P0131/P0134 (front A/F signal low or no activity), P0137 (rear O2 low voltage), and P0141 (heater circuit fault). The FSM provides pinpoint tests for wiring, heater resistance and sensor response using a scan tool and multimeter.

Should these sensors be replaced as routine maintenance?
They’re not strictly a scheduled item, but testing around 100,000–160,000 km is sensible if fuel economy drops or a MIL appears. If diagnostics show slow response or skewed trims, replacement with OEM‑spec parts is the smart move to protect the catalytic converter and keep emissions in check.