Parts for your 2022 Subaru Impreza-Knock sensor

2022 Subaru Impreza Knock Sensor — What It Does and When to Replace It

Based on Subaru factory service information for the 2022 model-year Impreza with the FB-series 2.0L engine (engine control system diagnostics covering DTCs P0325–P0328) and Subaru’s genuine parts catalogue for this VIN range, the vehicle is fitted with a block-mounted piezoelectric knock sensor. These technical references confirm the knock sensor’s role in monitoring combustion and enabling the ECU to control ignition timing to prevent knock (pinging) and safeguard the engine.

On a 2022 Subaru Impreza, the knock sensor listens for the sharp vibration signature of detonation. When it detects knock, the ECU trims ignition timing and, if needed, enriches the fuel mix to keep things smooth and safe. The pay-off is better drivability on Aussie and Kiwi petrol, improved fuel economy, lower emissions, and long engine life. It’s a small part doing a big job every time the driver rolls into the throttle.

There’s no scheduled replacement interval for the knock sensor, it’s a fit-and-forget item unless a fault crops up. The usual giveaway is the check engine light with codes like P0325 or P0328, a noticeable drop in power, rough running under load, or unusually high fuel use. Because the ECU plays it safe when it loses a reliable knock signal, performance can feel a bit doughy until the issue’s sorted.

Replacement is straightforward for a competent home mechanic, but space under the bonnet can be tight. Typical steps include disconnecting the battery, removing intake ducting for access, unplugging the sensor, undoing the single retaining bolt, cleaning the mounting pad on the block, then refitting the new sensor with the correct orientation and torque per the workshop manual. Over-tightening or twisting the body can damage the piezo element, so a torque wrench is a must. Route the harness exactly as from factory to avoid chafe.

Good practices during servicing: use quality 91 RON or better petrol, check the harness and connector for oil or coolant contamination, and keep an eye on live data (feedback knock/ignition correction) if a scan tool is handy. If a code appears, address basics first—fuel quality, intake leaks, and earths—then test or replace the sensor with the correct part number supersession for the vehicle’s VIN. After replacement, clear codes and road-test, the ECU will relearn trims over a few drive cycles.

• Common symptoms: CEL with P0325–P0328, lazy throttle response, pinging under load.
• Key tips: correct torque, correct orientation, genuine-quality part, clean mounting surface.

Popular questions

1) What are the signs a 2022 Impreza knock sensor is failing?
Drivers often notice the check engine light with a knock-sensor code, slightly sluggish performance, and sometimes pinging on hills. Fuel economy can slip because the ECU runs more conservative timing when the knock signal isn’t trustworthy. A scan tool showing persistent knock codes or abnormal knock correction is the clincher.

2) Is it safe to keep driving with a P0325 code?
It’ll usually run, but it’s not ideal. The ECU dials back timing to protect the engine, which hurts power and economy. Prolonged driving while the engine is actually knocking can risk piston or bearing damage. Best bet: check fuel quality, wiring, and replace the sensor if testing points that way.

3) Do I need to reprogram the ECU after replacing the sensor?
No programming is typically required. Clear the codes, then take it for a proper road test so the ECU can relearn timing trims. A few normal drive cycles should restore optimal performance if the underlying issue is resolved.