Parts for your 2006 Subaru Legacy-Knock sensor

2006 Subaru Legacy knock sensor — what it does, where it lives, and when to replace it

Based on the Subaru Factory Service Manual (2006 Legacy/Outback BL/BP, Engine section: Knock Sensor) and the Subaru genuine parts catalogue for MY2006, the 2006 Subaru Legacy is fitted with a knock sensor across its EJ-series engines (2.5i EJ253 and turbo EJ255/257). The FSM also documents OBD‑II DTCs P0325–P0330 for the knock sensor circuit, and the catalogue lists the part as Knock Sensor PN 22060AA061 (superseded by 22060AA070). So yes — this model absolutely uses a knock sensor and relies on it for proper ignition control.

The knock sensor’s job is simple but crucial: it listens for detonation (knock) in the engine and signals the ECU to tweak ignition timing to protect the pistons and keep the motor running sweet as. On the 2006 Legacy’s EJ engine, it’s bolted to the block under the intake, roughly central toward the rear of the engine bay beneath the bonnet. When it hears pinging from poor fuel, carbon build-up, or heavy load, it lets the ECU pull a touch of timing. That helps with reliability, smoothness, and fuel economy — especially important on Aussie and Kiwi summer days or when towing.

There’s no fixed service interval for the knock sensor, but it’s smart to check it whenever the intake is off or at big-ticket services (around 100,000–150,000 kilometres). Look for cracked wiring, a loose retaining bolt, corrosion on the block’s mating surface, or any physical damage. If replacement’s on the cards, go with a quality unit (genuine or reputable aftermarket), clean the mounting pad on the block, and tighten to the correct torque with a torque wrench. Don’t over‑tighten — the sensor is a piezo device and can be damaged if crushed. Make sure the locating tab/orientation matches the FSM notes so it “hears” correctly.

• Common symptoms of a crook knock sensor: check‑engine light (often P0325), sluggish performance, poor fuel economy, roughness under load, or the ECU holding timing back.
• Handy tips: use fresh fuel of the recommended octane, keep the cooling system healthy, and address intake leaks that can trigger false knock.

If you’ve had to replace the sensor, give the ECU a chance to relearn by taking the car for a varied drive cycle. If codes return, double‑check torque, orientation, wiring continuity, and the connector fit. Sorted properly, the Legacy’s knock control will keep the EJ happily humming for many more kays.

Technical references consulted: Subaru Factory Service Manual (2006 Legacy/Outback BL/BP, Engine/Diagnostics — Knock Sensor, DTC P0325–P0330), Subaru Genuine Parts Catalogue (MY2006 Legacy/Outback, Knock Sensor PN 22060AA061 → 22060AA070 supersession).

FAQ

Where is the knock sensor on a 2006 Subaru Legacy?
It’s mounted to the engine block under the intake manifold area, roughly central and toward the rear of the engine bay. Access is typically from above with the intake plumbing removed. On turbo models with more hardware up top, access can be tighter, but the location on the block is similar.

What are the signs of a failing knock sensor?
Expect a check‑engine light (often P0325), dulled performance, and sometimes worse fuel economy because the ECU keeps timing conservative. You might also notice hesitation under load. Physical inspection may reveal a cracked sensor body, damaged harness, or a loose mounting bolt.

Can you keep driving with a faulty knock sensor?
It’ll usually drive, but it’s not ideal. The ECU may pull timing to play it safe, which hurts performance and economy. In the worst case, genuine knock could go undetected. It’s best to diagnose and repair promptly to protect the EJ engine and keep the car running at its best.