Parts for your 2010 Subaru Impreza-Knock sensor

2010 Subaru Impreza knock sensor — what it does and how to look after it

Yes, the 2010 Subaru Impreza is factory-fitted with a knock sensor across the EJ25 2.5i and the turbo EJ255/EJ257 engines. This is documented in the Subaru Factory Service Manual (Engine Diagnostics listing DTCs P0325, P0327, P0328), Subaru’s genuine parts catalogue (knock sensor listed for 2010 Impreza variants), and independent data such as Autodata/Haynes and Mitchell1. So it’s absolutely relevant to servicing and reliability on this model.

The knock sensor is a piezoelectric microphone bolted to the engine block. It listens for high-frequency vibration from detonation (pinging) and lets the ECU trim ignition timing to protect the engine. That means better longevity, smoother performance on our Aussie and Kiwi fuels, and fewer emissions. On hot days, under load up a hill, or with lower-octane petrol, it’s the quiet achiever that keeps things safe.

• Signs it’s unhappy: check engine light with codes P0325/P0327/P0328, rattly pinging under load, flat spots, higher fuel use, or the ECU pulling timing so it feels sluggish.
• Common causes: cracked sensor housing, over‑tightened or dirty mounting surface, harness damage near the manifold, poor engine earths, or actual engine knock from carbon build-up or off-spec fuel.

It isn’t a routine replacement item, but it’s smart to inspect it during major services. Look for harness chafe, oil/coolant contamination, and make sure the mounting boss on the block is clean and corrosion‑free. If replacement is needed, go OEM or high‑quality equivalent, cheap copies can be noisy or miscalibrated.

1. Disconnect the battery and remove the intake snorkel/airbox for room.
2. Unplug the sensor and undo the single retaining bolt.
3. Clean the block’s mating surface, no sealant, just clean metal.
4. Install the new sensor in the correct orientation and tighten to the factory torque (per Subaru FSM) — do not over‑torque.
5. Route the loom exactly like OEM to avoid vibration damage and refit intake parts.
6. Clear codes, then road test under gentle load and check data for learned knock and timing advance.

If the light returns, chase root causes: fuel quality, intake leaks, carbon build‑up, or dodgy earths. A healthy knock sensor plus good fuel keeps the EJ nice and happy over hundreds of thousands of kilometres.

Popular questions

Where is the knock sensor on a 2010 Subaru Impreza?
It’s bolted to the top side of the block under the intake manifold, secured with a single bolt. On most EJ25s it’s easiest to reach from above after removing the intake snorkel or airbox. WRX/STI locations are similar, still under the manifold on the block’s upper deck.

How long should a knock sensor last?
Generally the life of the vehicle. Replace it only if it’s cracked, contaminated, out of spec, or throwing codes P0325/P0327/P0328. At major services, a quick visual check and loom inspection is all that’s needed.

Is it safe to drive with a bad knock sensor?
The car will usually run, but the ECU retards timing to play it safe. Power drops and fuel use goes up, and there’s risk that real knock isn’t managed properly. It’s best to sort it sooner rather than later.