Parts for your 2013 Subaru Impreza-Knock sensor

2013 Subaru Impreza Knock Sensor

The 2013 Subaru Impreza is fitted with a knock sensor. This is confirmed by Subaru’s factory service information for the GJ/GP series (FB20 engine) which details knock-sensor diagnostics and ECU control strategy, common OBD-II fault codes like P0325/P0328 that specifically reference the knock sensor circuit, and the official Subaru parts catalogue which lists a knock sensor for this model. So yes—this part is relevant, present, and important on a 2013 Impreza.

On this Impreza, the knock sensor’s job is to listen for detonation (that metallic “ping”) and let the engine computer trim ignition timing to keep things smooth and safe. It helps the FB20 run efficiently on everyday fuel, protects the engine under load, and can even adapt to varying fuel quality. When it’s healthy, drivers get better driveability, decent fuel economy, and less risk of long-term engine stress from unchecked knock.

It’s not a routine replacement item, but it’s worth a look during servicing. Keep an eye out for damaged wiring, brittle connectors, or signs of coolant or oil contamination around the mounting area on the block. If the Check Engine light pops up with a knock-sensor code, don’t ignore it—the ECU may drop into a conservative timing map, which can sap power and bump up fuel use.

• Common clues it’s unhappy:
  • Check Engine light with codes like P0325/P0328
  • Sluggish performance or poor economy
  • Occasional ping under load (especially up hills)

Replacement is straightforward for a trained tech. The sensor sits bolted to the engine block, beneath the intake area. The mounting face must be clean and dry—no grease or sealant—so it can “hear” the block properly. Use the correct torque (around 24 N·m is typical for Subaru knock sensors) and orient the connector as specified in the service manual, over-tightening or misalignment can cause false readings. Always route the harness away from high electrical noise and sharp edges, then clear codes and road-test so the ECU can relearn. Genuine or high-quality aftermarket sensors are recommended—cheap units can be noisy and trigger nuisance faults. Day to day, there’s nothing special to do, just stick to quality fuel, keep the cooling system in good nick, and let the sensor and ECU do the clever bits in the background.

Where is the knock sensor on a 2013 Impreza?

It’s mounted on the engine block under the intake side of the FB20. Access is from above with intake components moved aside, or from the side depending on tooling. The single bolt passes through the sensor’s metal eyelet into the block, with the connector pointing in a set direction per the service manual.

Does it need regular replacement?

No, it’s not a scheduled service item. Replace it only if it’s failed testing, shows damage, or there’s a confirmed DTC like P0325/P0328 after wiring checks. Many last the life of the vehicle if the mounting is clean and the harness is tidy.

Is it safe to drive with a bad knock sensor?

Best avoided. The ECU may run a safe, power-reducing timing map, which can make the car feel doughy and burn more fuel. If actual knock occurs and the sensor can’t report it, long-term engine wear is possible. Get it diagnosed and sorted promptly.