Parts for your 2020 Subaru Outback-Knock sensor

2020 Subaru Outback knock sensor: what it does and when to replace it

Based on technical documentation, the 2020 Subaru Outback is fitted with a knock sensor. The Subaru Factory Service Manual (Engine and Diagnostics sections for the 2020 Outback/Legacy platform) details the knock sensor’s role in the Engine Control Module strategy and includes wiring diagrams for the sensor circuit. Subaru’s official parts catalogue for the 2020 Outback (covering both the 2.5‑litre FB25 and the 2.4‑litre turbo FA24 models) also lists a knock sensor as a service part, and OBD‑II diagnostic coverage includes knock sensor fault codes (e.g., P0325, P0328). That makes the knock sensor very much relevant to this model.

On this Outback, the knock sensor listens for the high‑frequency vibration signatures of detonation (knock) in the engine block. When it detects knock, the ECU trims ignition timing and, if needed, adjusts fuelling to protect the engine. That lets the car run smoothly on real‑world Aussie and Kiwi fuels, helps power and economy, and reduces emissions without risking the motor.

Typical signs of a crook knock sensor or circuit include a Check Engine light with codes like P0325/P0328, rough running, lazy performance, higher fuel use, or even audible pinging under load. The ECU may jump to a conservative timing map to keep things safe, so it’ll drive, but it won’t feel its best.

It’s not a scheduled maintenance item, but it deserves a look during regular servicing. A quick visual check for a damaged connector, brittle loom, oil contamination, or anything rubbing on the harness can save headaches later. Keeping the top of the block clean around the sensor mount helps, too. Avoid “tap tests” on the block—modern sensors and ECUs don’t love that sort of backyard trick.

If replacement is needed, go with a genuine or high‑quality equivalent sensor. The unit bolts to the engine block and relies on a clean, flat mating surface, the correct orientation, and exact torque as specified in the Subaru service manual. Over‑ or under‑tightening can throw off readings. After fitting, clear any DTCs, check live data, and road‑test through a few kilometres of mixed driving so the ECU can relearn knock control. If a code returns, check harness continuity, grounds, and ECU pins before blaming the new sensor. Most workshops can sort this in well under an hour with no dramas.

• Common DTCs: P0325 (Knock Sensor Circuit), P0328 (Knock Sensor High Input)
• Best practice: clean mount, correct orientation, torque to spec, quality part
• Good habit at each service: inspect loom/connector and nearby oil leaks

Popular questions about the 2020 Subaru Outback knock sensor

Does the 2020 Outback actually have a knock sensor?
Yes. Both the 2.5‑litre FB25 and the 2.4‑litre turbo FA24 models use a block‑mounted knock sensor tied into the ECU’s ignition control strategy. This is documented in the Subaru Factory Service Manual and reflected in the OEM parts catalogue and diagnostic procedures.

Where is the knock sensor on a 2020 Outback?
It’s mounted to the engine block under the intake manifold area. Access and exact position vary slightly between the FB25 and FA24 engines, but expect it near the centre‑rear portion of the block with a single retaining bolt and a two‑wire connector. A workshop manual is handy for precise orientation and torque.

Is it OK to keep driving with a knock sensor fault code?
The car will usually run, but the ECU may pull timing, making it feel flat and thirsty. Continued driving risks poor performance and, if detonation goes unchecked due to a sensor or wiring fault, potential engine damage. Best bet is to diagnose and repair promptly so it’s back to running sweet.