Parts for your 2014 Subaru Impreza-Knock sensor

2014 Subaru Impreza knock sensor — fitted, useful, and worth keeping healthy

Yes, the 2014 Subaru Impreza is fitted with a knock sensor. Factory documentation (2014MY Impreza Factory Service Manual — Engine/Diagnostics sections covering DTC P0325–P0328 Knock Sensor Circuit, and Subaru Technical Information System) specifies a piezoelectric knock sensor mounted to the FB20 engine block, used by the engine control module (ECM) to detect detonation and adjust ignition timing.

On this model, the knock sensor “listens” for high-frequency vibration caused by spark knock (pinging). When it hears knock, the ECM trims timing to protect the pistons and keep the engine running smoothly on Aussie and Kiwi petrol, whether it’s a summer scorcher or a chilly alpine morning. It’s one of those quiet heroes that helps fuel economy, drivability, and engine longevity under the bonnet.

It’s generally not a scheduled replacement item, but it’s smart to consider it during servicing if there are symptoms or fault codes. Common tell-tales include the check engine light with codes like P0325/P0327/P0328, lacklustre performance, increased fuel use, or audible pinging on load. Because the sensor sits bolted to the block (typically beneath the intake area), heat and age can harden the wiring or affect the sensor’s response over high kilometres.

• Inspection tips: Look for damaged wiring, loose connectors, and oil or coolant contamination around the sensor mount. Any corrosion or debris between the sensor and block can dull sensitivity.
• Replacement best practice: Use an OEM-quality sensor, fit it to a clean, bare-metal mounting pad, orient the connector as per the service manual, and torque the retaining bolt to the factory spec. Over- or under‑torque can skew readings.
• After fitting: Clear fault codes, verify no recurrences, and perform any idle/ECM relearn steps recommended in the Subaru service procedures.

A healthy knock sensor lets the ECM run timing closer to the sweet spot for power and economy while still protecting the engine on ordinary 91 RON or when fuel quality varies on a road trip. If the vehicle has racked up plenty of kilometres, has had prior engine bay work, or shows intermittent knock-related codes, it’s worth a closer look during a service. A straightforward swap with the right spanner work and attention to cleanliness and torque spec will have it back to doing its quiet, clever job.

FAQs

Where is the knock sensor on a 2014 Subaru Impreza?
It’s bolted to the FB20 engine block, beneath the intake area. Access usually involves removing intake ducting or related components to reach the single sensor and its loom. Refer to the factory manual’s Engine section for the exact view and connector routing.

What are the symptoms of a failing knock sensor?
Drivers may see a check engine light (often P0325/P0327/P0328), notice flat performance, increased fuel use, or hear pinging under load. Sometimes there’s no noise at all—the ECM just pulls timing to stay safe, and the car feels a bit lazy.

Do I replace it as routine maintenance?
No, it’s not a routine item. Replace it if it’s faulty, contaminated, damaged, or flagging codes. When replacing, use an OEM-spec part, clean the mounting pad, and torque to spec from the Subaru service manual.