Parts for your 2007 Subaru Legacy-Knock sensor

2007 Subaru Legacy knock sensor — what it does and how to look after it

Yes, the 2007 Subaru Legacy (BL/BP) is fitted with a knock sensor on its petrol EJ-series engines (EJ20/EJ25). This is confirmed in the Subaru Legacy/Outback factory service manual for 2005–2009 models under OBD-II diagnostics (DTC P0325/P0327/P0328 Knock Sensor Circuit), the Engine (Mechanical) section showing the sensor mounted on the cylinder block, and the Subaru parts catalogue listing the knock sensor (commonly p/n 22060AA061, superseded to 22060AA070 in some markets). Those technical sources describe its role, location, faults and replacement details.

On the 2007 Legacy, the knock sensor is a piezo unit bolted to the top-rear of the engine block. It listens for detonation (that metallic “ping” under load) and signals the ECU to trim ignition timing to protect the engine. That means better reliability on hot days, under heavy throttle, and with variable fuel quality around Australia and New Zealand. If it’s happy, you get smooth power and decent economy, if it’s grumpy or dead, you can cop rough running, poor fuel economy, and a check engine light with codes like P0325, P0327 or P0328.

Replacement is straightforward for a competent DIYer. Under the bonnet, the sensor sits on the block near the bellhousing. Disconnect the battery negative, unplug the connector, and remove the single mounting bolt. Clean the mating surface on the block so the new sensor can “hear” properly. Fit the new genuine sensor, orient it as per the manual (connector facing forward), and torque the bolt accurately to about 24 N·m (don’t overtighten). No sealant or grease on the contact face or threads. Reconnect, clear codes, and let the ECU relearn over a few drives.

As part of regular servicing, it’s worth a quick visual once-over: check for cracks in the sensor body, corrosion on the connector, or a chafed harness. If the car pings under load, feels flat, or logs knock sensor codes, don’t ignore it—detonation can be harsh on pistons and head gaskets. Use good quality fuel, keep the cooling system healthy, and stick with an OEM sensor, cheap copies can be too sensitive or not sensitive enough, throwing timing off and costing you power and fuel.

• Technical sources referenced: Subaru Legacy/Outback 2005–2009 Factory Service Manual (Engine Diagnostics, DTC P0325/P0327/P0328, Engine Mechanical section for installation/torque), and Subaru MY2007 parts catalogue (Engine Electrical group, knock sensor p/n 22060AA061/22060AA070).

FAQ — Where is the knock sensor on a 2007 Subaru Legacy?

It’s bolted to the top-rear of the engine block, roughly central near the bellhousing. You can usually see it from above with the intake snorkel out of the way—one 12 mm bolt and a single two-pin connector.

FAQ — Is it safe to drive with a faulty knock sensor?

Short trips may be possible, but it’s not ideal. With a bad signal the ECU may pull timing and the car can feel sluggish and thirsty, or worse, it may not catch detonation quickly. Sort it sooner rather than later to avoid potential engine damage.

FAQ — What torque and orientation does the sensor need?

Torque is about 24 N·m on EJ engines, and the sensor should be oriented with the connector facing forward (per factory manual). Clean the block surface, don’t use grease or sealant, and don’t twist the harness when tightening.