Parts for your 2015 Subaru Impreza-Knock sensor

2015 Subaru Impreza Knock Sensor — What It Does and How to Look After It

Yes, the 2015 Subaru Impreza is fitted with a knock sensor. Technical references confirm it: the Subaru factory service information for the 2015 MY Impreza (FB20 engine) includes diagnostics for Knock Sensor Circuit (DTCs P0325, P0327 and P0328), and the genuine parts catalogue lists a dedicated knock sensor for this model. These sources establish that the knock sensor is an integral part of the engine management system on this vehicle.

The knock sensor’s job is straightforward but critical. It “listens” for abnormal combustion (detonation or pinging) through a piezoelectric element bolted to the engine block. When knock is detected, the engine control unit trims ignition timing to protect the pistons, rings and bearings. The result is smoother running, better longevity and the best mix of performance and fuel economy the Impreza can safely deliver on Aussie and Kiwi petrol, whether that’s regular 91 RON or premium 95/98.

For servicing, the knock sensor isn’t a regular replacement item like spark plugs or filters. It’s generally a fit-and-forget component, but it pays to keep an eye on it at major services, especially past 100,000 kilometres. Under the bonnet, it sits on the engine block beneath the intake manifold, so visual checks focus on the connector and harness: look for brittle insulation, oil contamination, corrosion or signs of rodent or heat damage. If the check engine light pops up with P0325, P0327 or P0328, a proper diagnosis should confirm wiring integrity, correct sensor mounting, and that the sensor hasn’t been over‑ or under‑torqued.

Replacement is straightforward for a trained tech. Key points:

• Use a quality OE-equivalent or genuine sensor and clean the mounting pad on the block.
• Align and torque the sensor to Subaru spec with a torque wrench, don’t twist the pigtail.
• Clear codes and allow the ECU to relearn knock control over a normal drive cycle.

Owners might notice symptoms of a crook knock sensor such as reduced power, lazier throttle response, poorer fuel economy and the MIL on. Because the ECU will often pull timing to stay safe, audible pinging may not be obvious, which is why scanning for codes and checking live data is the smart approach.

FAQs

Where is the knock sensor on a 2015 Subaru Impreza?
It’s mounted on the engine block under the intake manifold, roughly central on the block. Access usually requires removing intake components for a clear line of sight.

Is it safe to drive with a faulty knock sensor?
The ECU will typically retard timing to protect the engine, so the car will run but with less power and higher fuel use. Prolonged driving isn’t recommended, as genuine knock may go unmanaged, risking engine damage if other issues are present.

Does a new knock sensor need coding?
No special coding is required. After fitting, clear any fault codes and allow the ECU to relearn over normal driving. Many techs also recommend using good quality petrol during the relearn period.